Thyroid Function Rather Than Thyroid Antibodies Affects Pregnancy and Perinatal Outcomes: Results of a Prospective Study

CONTEXT

Thyroid autoantibody positivity has been associated with an increased rate of obstetrical complications.

OBJECTIVE

We aimed to evaluate the role of thyroid autoantibodies in adverse pregnancy outcomes.

METHODS

This prospective study was conducted in the Endocrinology Unit of Pisa Hospital. A total of 975 pregnant women were studied from 2012 to 2021; 572 (59%) were diagnosed with autoimmune thyroid (AT) diseases; 403 (41%) served as controls. Levothyroxine (LT4) treatment was introduced when TSH was > 2.5 mIU/L in the AT group and when TSH was > 4 mIU/L in the controls. Rates of obstetrical complications in each group were measured.

RESULTS

Although the frequency of miscarriage in the AT group was greater (4.8%) than in the controls (2.9%), no significant differences were detected (P = 0.181). There were no differences between the 2 groups concerning the other pregnancy complications, and no association with the titer of thyroid antibodies was observed. The frequency of congenital malformations was greater in the AT group than in the controls (P = 0.019), but no correlation with major congenital malformations was detected (P = 0.872). Given that thyroid hormone concentrations were strictly controlled in our population, we documented a tendency (not significant) toward an increase in miscarriage and preterm birth among women with TSH > 4 mIU/L.

CONCLUSION

If thyroid function is adequately controlled, the presence and titer of thyroid autoantibodies does not negatively influence gestation. Although not significant, suboptimal thyroid hormone status seems to affect pregnancy outcomes more than thyroid autoimmunity.

OR11-3 Steroid Treatment in the Management of Destructive Thyrotoxicosis Induced by PD1 Blockade

Background

Destructive thyroiditis is the most common endocrine immune related adverse event (iRAEs) in patients treated with anti-PD1/PD-L1 agents. Given its self-limited course, current guidelines recommend no treatment for this iRAE. Nevertheless in patients with enlarged thyroid volume and a poor performance status, thyrotoxicosis may be particularly severe and harmful. Aim of the study is to evaluate if steroid treatment might be useful in improving thyrotoxicosis in subjects with a poor performance status.

Methods

We conducted a case-control study, comparing the course of thyrotoxicosis of 4 patients treated with oral prednisone at the dosage of 25 mg/d (tapered to discontinuation in three weeks) and an enlarged thyroid volume to that of 8 patients with similar thyroid volume who were left untreated.

Results

No difference was found between the two groups at the onset of thyrotoxicosis (time 0) in demographic characteristics and in the levels of thyroid hormones. The levels of thyroid hormones were lower in subjects treated with prednisone compared to those untreated at time 7, 14, 21, 28, 35, 42, 60 and 90 days (P<0.05 at each time). The median time to remission of thyrotoxicosis was 24 days in patients treated with steroids and 92 days in untreated patients (P<0.001). At 6 months, the rate of evolution to hypothyroidism was similar in the 2 groups (4/4 in steroid group vs 7/8 in untreated group, P=0.74) and no difference was found in tumor progression (Progression free survival in treated group 5.1 months vs 5.0 months in untreated patients, P=0.89).

Conclusion

A short period of prednisone therapy is useful to restore more quickly euthyroidism in patients with a poor performance status and a severe destructive thyrotoxicosis induced by PD-1 blockade. This treatment does not impair the efficacy of immunotherapy.

Presentation: Sunday, June 12, 2022 11:30 a.m. - 11:45 a.m.

Steroid treatment in the management of destructive thyrotoxicosis induced by PD1 blockade

Objective

Destructive thyroiditis is the most common endocrine immune-related adverse event (iRAEs) in patients treated with anti-PD1/PD-L1 agents. Given its self-limited course, current guidelines recommend no treatment for this iRAE. Nevertheless, in patients with enlarged thyroid volume and a poor performance status, thyrotoxicosis may be particularly severe and harmful. The aim of the study is to evaluate if steroid treatment might be useful in improving thyrotoxicosis in subjects with a poor performance status.

Methods

We conducted a retrospective study, comparing the course of thyrotoxicosis of four patients treated with oral prednisone at the dosage of 25 mg/day (tapered to discontinuation in 3 weeks) and an enlarged thyroid volume to that of eight patients with similar thyroid volume who were left untreated.

Results

The levels of thyroid hormones were lower in subjects treated compared to those untreated at time of 7, 14, 21, 28, 35, 42, 60 and 90 days (P < 0.05 at each time). The time to remission of thyrotoxicosis was 24 days in patients treated with steroids and 120 days in untreated patients (P < 0.001). At 6 months, the rate of evolution to hypothyroidism was similar in the two groups (4/4 in the steroid group vs 7/8 in the untreated group, P = 0.74) and no difference was found in tumor progression (P = 0.89).

Conclusions

Our preliminary data suggest that in patients with a poor performance status experiencing a severe destructive thyrotoxicosis induced by PD-1 blockade, a short period of administration of oral prednisone is effective in obtaining a quick reduction of the levels of thyroid hormones.

Gene expression profile in functioning and non-functioning nodules of autonomous multinodular goiter from an area of iodine deficiency: unexpected common characteristics between the two entities

PURPOSE

Toxic multinodular goiter is a heterogeneous disease associated with hyperthyroidism frequently detected in areas with deficient iodine intake, and functioning and non-functioning nodules, characterized by increased proliferation but opposite functional activity, may coexist in the same gland. To understand the distinct molecular pathology of each entity present in the same gland, the gene expression profile was evaluated by using the Affymetrix technology.

METHODS

Total RNA was extracted from nodular and healthy tissues of two patients and double-strand cDNA was synthesized. Biotinylated cRNA was obtained and, after chemical fragmentation, was hybridized on U133A and B arrays. Each array was stained and the acquired images were analyzed to obtain the expression levels of the transcripts. Both functioning and non-functioning nodules were compared versus healthy tissue of the corresponding patient.

RESULTS

About 16% of genes were modulated in functioning nodules, while in non-functioning nodules only 9% of genes were modulated with respect to the healthy tissue. In functioning nodules of both patients and up-regulation of cyclin D1 and cyclin-dependent kinase inhibitor 1 was observed, suggesting the presence of a possible feedback control of proliferation. Complement components C1s, C7 and C3 were down-regulated in both types of nodules, suggesting a silencing of the innate immune response. Cellular fibronectin precursor was up-regulated in both functioning nodules suggesting a possible increase of endothelial cells. Finally, Frizzled-1 was down-regulated only in functioning nodules, suggesting a role of Wnt signaling pathway in the proliferation and differentiation of these tumors. None of the thyroid-specific gene was deregulated in microarray analysis.

CONCLUSION

In conclusion, the main finding from our data is a similar modulation for both kinds of nodules in genes possibly implicated in thyroid growth.

Circulating Levels of MiRNAs From 320 Family in Subjects With Lipodystrophy: Disclosing Novel Signatures of the Disease

Lipodystrophy (LD) indicates a group of rare disorders, with generalized or partial loss of white adipose tissue (WAT) often associated with metabolic derangements. Heterogeneity/wide spectrum of the disease and lack of biomarkers make diagnosis often difficult. MicroRNAs are important to maintain a correct WAT function and WAT is a source of circulating miRNAs (cmiRs). miRNAs from 320 family were previously detected in the WAT and variably associated to the metabolic syndrome. Our aim was then to investigate if LD can result in altered abundance of cmiRs-320. We collected samples from a cohort of LD subjects of various subtypes and from age matched controls. Use of quantitative PCR determined that cmiRs- 320a-3p, 320b, 320c, 320e are upregulated, while 320d is downregulated in LD. CmiRs-320 power as classifiers was more powerful in the most extreme and defined forms of LD, including the generalized and the Dunnigan subtypes. cmiR-320a-3p showed significant inverse relationships with plasma leptin (P < 0.0001), typically low in LD. The hepatic enzymes gamma-glutamyl transferase (GGT), aspartate aminotransferase (AST), alanine aminotransferase (ALT) and the marker of inflammation C-reactive protein (CRP) were inversely related to cmiR 320d (P < 0.05, for CRP and GGT; P < 0.01, for AST and ALT). Gene ontology analysis revealed cell-cell adhesion as a process regulated by 320 miRNAs targets, thus disclosing a novel route to investigate origin of WAT loss/dysfunction. In conclusion, cmiRs-320 constitute novel biomarkers of LD, abundance of miR320a-3p is inversely associated to indicators related to WAT function, while downregulation of cmiR-320d predicts an altered hepatic profile and higher inflammation.

Management of Thyrotoxicosis Induced by PD1 or PD-L1 Blockade

Context

Thyrotoxicosis is a common immune-related adverse event in patients treated with programmed cell death protein-1 (PD1) or programmed cell death protein ligand-1 (PD-L1) blockade. A detailed endocrinological assessment, including thyroid ultrasound and scintigraphy, is lacking, as are data on response to treatment and follow-up.

Objective

The aim of this study was to better characterize the thyrotoxicosis secondary to immune checkpoint inhibitors, gaining insights into pathogenesis and treatment.

Methods

We conducted a retrospective study of 20 consecutive patients who had normal thyroid function before starting immunotherapy and then experienced thyrotoxicosis on PD1 or PD-L1 blockade. Clinical assessment was combined with thyroid ultrasound, ^99mtechnecium scintiscan, and longitudinal thyroid function tests.

Results

Five patients had normal or increased scintigraphic uptake (Sci+), no serum antibodies against the thyrotropin receptor, and remained hyperthyroid throughout follow-up. The other 15 patients had no scintigraphic uptake (Sci–) and experienced destructive thyrotoxicosis followed by hypothyroidism (N = 9) or euthyroidism (N = 6). Hypothyroidism was more readily seen in those with normal thyroid volume than in those with goiter (P = .04). Among Sci– individuals, a larger thyroid volume was associated with a longer time to remission (P < .05). Methimazole (MMI) was effective only in Sci+ individuals (P < .05).

Conclusion

Administration of PD1- or PD-L1–blocking antibodies may induce 2 different forms of thyrotoxicosis that appear similar in clinical severity at onset: a type 1 characterized by persistent hyperthyroidism that requires treatment with MMI, and a type 2, characterized by destructive and transient thyrotoxicosis that evolves to hypothyroidism or euthyroidism. Thyroid scintigraphy and ultrasound help in differentiating and managing these 2 forms of iatrogenic thyrotoxicosis.

Management of Thyrotoxicosis Induced by PD1 or PD-L1 Blockade

Context: Thyrotoxicosis is a common immune-related adverse event in patients treated with PD1 or PD-L1 checkpoint inhibitors. A detailed endocrinological assessment, including thyroid ultrasound and scintigraphy is missing, as are data on response to treatment and follow-up. Objectives: To better characterize the thyrotoxicosis secondary to immune checkpoint inhibitors, gaining insights into pathogenesis and informing management. Methods: We conducted a prospective cohort study of 20 consecutive patients who had normal thyroid function before starting immunotherapy and then experienced thyrotoxicosis upon PD1 or PD-L1 blockade. Clinical assessment was combined with thyroid ultrasound, scintigraphy, and longitudinal thyroid function tests. Results: Five patients had normal scintigraphic uptake (Sci+), no serum antibodies against the TSH receptor, and remained hyperthyroid throughout follow-up. The other 15 patients had no scintigraphic uptake (Sci-) and experienced destructive thyrotoxicosis followed by hypothyroidism (N= 9) or euthyroidism (N= 6). Hypothyroidism was more readily seen in those with normal thyroid volume than in those with goiter (P= 0.04). Among Sci- subjects, a larger thyroid volume was associated to a longer time to remission (P&lt;0.05). Methimazole (MMI) was effective only in Sci+ subjects (P&lt;0.05). Conclusions: Administration of PD1 or PD-L1 blocking antibodies may induce two different forms of thyrotoxicosis that appear similar in clinical severity at onset: a type 1 characterized by persistent hyperthyroidism that requires treatment with MMI, and a type 2 characterized by destructive and transient thyrotoxicosis that evolves to hypo- or eu-thyroidism. Thyroid scintigraphy and ultrasound help differentiating and managing these two forms of iatrogenic thyrotoxicosis

The Role of Nuclear Medicine in the Clinical Management of Benign Thyroid Disorders, Part 2: Nodular Goiter, Hypothyroidism, and Subacute Thyroiditis

Part 2 of this series of Continuing Education articles on benign thyroid disorders deals with nodular goiter, hypothyroidism, and subacute thyroiditis. Together with Part 1 (which dealt with various forms of hyperthyroidism), this article is intended to provide relevant information for specialists in nuclear medicine dealing with the clinical management of patients with benign thyroid disorders, the primary audience for this series. Goiter, an enlargement of the thyroid gland, is a common endocrine abnormality. Constitutional factors, genetic abnormalities, or dietary and environmental factors may contribute to the development of nodular goiter. Most patients with nontoxic nodular goiter are asymptomatic or have only mild mechanical symptoms (globus pharyngis). Work-up of these patients includes measurement of thyroid-stimulating hormone, free triiodothyronine, free thyroxine, thyroid autoantibodies, ultrasound imaging, thyroid scintigraphy, and fine-needle aspiration biopsy of nodules with certain ultrasound and scintigraphic features. Treatment for multinodular goiter includes dietary iodine supplementation, surgery, radioiodine therapy (to decrease thyroid size), and minimally invasive ablation techniques. Hypothyroidism ranges from rare cases of myxedema to more common mild forms (subclinical hypothyroidism). Primary hypothyroidism often has an autoimmune etiology. Clinical presentations differ in neonates, children, adults, and elderly patients. Work-up includes thyroid function tests and ultrasound imaging. Nuclear medicine is primarily used to locate ectopic thyroid tissue in congenital hypothyroidism or to detect defects in iodine organification with the perchlorate discharge test. Treatment consists of thyroid replacement therapy with l-thyroxine, adjusting the daily dose to the individual patient's metabolic and hormonal requirements. Subacute thyroiditis is a self-limited inflammatory disorder of the thyroid gland, often associated with painless or painful swelling of the gland and somatic signs or symptoms. Inflammation disrupts thyroid follicles resulting in a rapid release of stored thyroxine and triiodothyronine causing an initial thyrotoxic phase, often followed by transient or permanent hypothyroidism. Although subacute thyroiditis is often related to a viral infection, no infective agent has been identified. Subacute thyroiditis may be caused by a viral infection in genetically predisposed individuals. Work-up includes lab tests, ultrasound imaging, and radionuclide imaging. Thyroid scintigraphy demonstrates different findings depending on the phase of the illness, ranging from very low or absent tracer uptake in the thyroid gland in the hyperthyroid phase to a normal appearance in the late recovery phase. Since subacute thyroiditis is self-limited, treatment is directed toward relief of pain. High-dose nonsteroidal antiinflammatory drugs are usually the first-line treatment. If severe pain persists, a course of corticosteroids may be necessary. Permanent hypothyroidism develops in up to 15% of patients with subacute thyroiditis, even more than 1 y after presentation.

Graves' Disease Induced by Immune Checkpoint Inhibitors: A Case Report and Review of the Literature

INTRODUCTION

In the last few years, immune checkpoint inhibitors (ICPis) have become a common treatment of cancer. ICPis are associated with peculiar immune side effects, termed immune-related adverse events (irAEs). Thyroid disfunction is a common irAE, but clinical manifestation, severity, and pathogenesis can be variable. While destructive thyroiditis and hypothyroidism are the most common thyroid irAEs induced by ICPis, autoimmune hyperthyroidism (Graves' disease) is rare. We describe a case of a Graves' disease induced by anti-PD-1 therapy and we review the previous reports on this issue.

CASE PRESENTATION

A 51-year-old man developed an overt autoimmune hyperthyroidism 2 months after he had started nivolumab (anti-PD-1) therapy for a metastatic non-small cell lung cancer. Although TSH-receptor autoantibodies (TRAb) were negative, the persistence of hyperthyroidism, the hypervascular pattern at thyroid ultrasound, and the high uptake at thyroid scintigraphy were all features suggestive of Graves' disease. Methimazole was started with the prompt restoration of euthyroidism. TRAb remained undetectable during the entire follow-up.

CONCLUSIONS

Autoimmune hyperthyroidism can be induced by anti-PD-1 treatment. TRAb were negative in both cases of nivolumab-induced Graves' disease described to date. A correct differential diagnosis between destructive thyroiditis and autoimmune hyperthyroidism is crucial for the appropriate treatment.

Thyroglobulin autoantibodies switch to immunoglobulin (Ig)G1 and IgG3 subclasses and preserve their restricted epitope pattern after 131I treatment for Graves' hyperthyroidism: the activity of autoimmune disease influences subclass distribution but not epitope pattern of autoantibodies

The subclass distribution of thyroglobulin autoantibodies (TgAb) is debated, whereas their epitope pattern is restricted. Radioidine ((131)I) treatment for Graves' disease (GD) induces a rise in TgAb levels, but it is unknown whether it modifies subclass distribution and epitope pattern of TgAb as well. We collected sera from GD patients before (131) I treatment and 3 and 6 months thereafter. We measured total TgAb, TgAb light chains and TgAb subclasses by enzyme-linked immunosorbent assay (ELISA) in 25 patients. We characterized the TgAb epitope pattern in 30 patients by inhibiting their binding to (125-) (I) Tg by a pool of four TgAb-Fab (recognizing Tg epitope regions A, B, C and D) and to Tg in ELISA by each TgAb-Fab. Total TgAb immunoglobulin (Ig)G rose significantly (P = 0.024). TgAb κ chains did not change (P = 0.052), whereas TgAb λ chains increased significantly (P = 0.001) and persistently. We observed a significant rise in IgG1 and IgG3 levels after (131)I (P = 0.008 and P = 0.006, respectively), while IgG2 and IgG4 levels did not change. The rise of IgG1 was persistent, that of IgG3 transient. The levels of inhibition of TgAb binding to Tg by the TgAb-Fab pool were comparable. A slight, non-significant reduction of the inhibition by the immune-dominant TgAb-Fab A was observed 3 and 6 months after (131)I. We conclude that (131)I treatment for GD increases the levels of the complement-activating IgG1 and IgG3 subclasses and does not influence significantly the epitope pattern of TgAb. In autoimmune thyroid disease subclass distribution of autoantibodies is dynamic in spite of a stable epitope pattern.

The different requirement of L-T4 therapy in congenital athyreosis compared with adult-acquired hypothyroidism suggests a persisting thyroid hormone resistance at the hypothalamic-pituitary level

BACKGROUND

Levothyroxine (l-T4) is commonly employed to correct hormone deficiency in children with congenital hypothyroidism (CH) and in adult patients with iatrogenic hypothyroidism.

OBJECTIVE

To compare the daily weight-based dosage of the replacement therapy with l-T4 in athyreotic adult patients affected by CH and adult patients with thyroid nodular or cancer diseases treated by total thyroidectomy.

DESIGN AND METHODS

A total of 36 adult patients (27 females and nine males) aged 18-29 years were studied; 13 patients (age: 21.5±2.1, group CH) had athyreotic CH treated with l-T4 since the first days of life. The remaining 23 patients (age: 24±2.7, group AH) had hypothyroidism after total thyroidectomy (14 patients previously affected by nodular disease and nine by thyroid carcinoma with clinical and biochemical remission). Patient weight, serum free thyroid hormones, TSH, thyroglobulin (Tg), anti-Tg, and anti-thyroperoxidase antibodies were measured. Required l-T4 dosage was evaluated. At the time of the observations, all patients presented free thyroid hormones within the normal range and TSH between 0.8 and 2 μIU/ml.

RESULTS

Patients had undetectable Tg and anti-thyroid antibodies. The daily weight-based dosage of the replacement therapy with l-T4 to reach euthyroidism in patients of group CH was significantly higher than that in those of group AH (2.16±0.36 vs 1.73±0.24 μg/kg, P<0.005). Patients of group CH treated with l-T4 had significantly higher serum TSH levels than patients of group AH (P=0.05) as well as higher FT4 concentrations.

CONCLUSIONS

To correct hypothyroidism, patients of group CH required a daily l-T4 dose/kg higher than group AH patients, despite higher levels of TSH. The different requirement of replacement therapy between adult patients with congenital and those with surgical athyroidism could be explained by a lack of thyroid hormones since fetal life in CH, which could determine a different set point of the hypothalamus-pituitary-thyroid axis.

Frequency and effect on serum TSH of phosphodiesterase 8B (PDE8B) gene polymorphisms in patients with sporadic nonautoimmune subclinical hypothyroidism

BACKGROUND

Nonautoimmune subclinical hypothyroidism (NSH) is characterized by elevated serum TSH in presence of normal thyroid hormone levels and absence of anti-thyroid antibodies. As result of a genomic-wide study, a strong association between three polymorphic variants in intron 1 of human PDE8B gene (rs4704397, rs6885099, rs2046045) and serum TSH has been reported in euthyroid subjects.

AIM

The aim of this study was to evaluate frequency and effects on serum TSH of PDE8B gene polymorphisms in patients with sporadic NSH and verify if differences in serum TSH levels are associated to these polymorphic variants.

SUBJECTS AND METHODS

A total of 58 Italian selected patients affected by NSH, with elevated serum TSH, normal FT3 and FT4 and without TSHr gene mutations, were subjected to genotyping for specific single nucleotide polymorphism of PDE8B gene.

RESULTS

In all patients, the integrity of TSH receptor gene was attested. The ancestral allele associated with increased serum TSH was present in 42/58 patients (72.4 %) for rs4704397, in 42/58 patients (72.4 %) for rs6885099 and in 44/58 patients (75.9 %) for rs2046045. However, similar values of serum TSH were detected in patients with minor or major allele for each polymorphism.

CONCLUSIONS

A prevalence of the minor allele of PDE8B gene polymorphism associated with elevated serum levels of TSH was demonstrated in patients affected by sporadic NSH; however, significant differences in circulating TSH in patients with minor or major alleles for each polymorphism were not identified demonstrating the lack of association between the polymorphisms and serum TSH levels in these patients.

Iodine contributes to thyroid autoimmunity in humans by unmasking a cryptic epitope on thyroglobulin

CONTEXT

The mechanisms linking thyroid autoimmunity and iodine use in humans are unknown.

OBJECTIVE

Our aim was to correlate iodine intake, thyroid autoimmunity, and recognition of thyroglobulin (Tg) epitopes after implementation of iodine prophylaxis.

SETTING

The general community living in an Italian village was evaluated.

MAIN OUTCOME MEASURES

Thyroglobulin autoantibodies (TgAb), thyroperoxidase autoantibodies (TPOAb), and urinary iodine excretion were assessed in 906 iodized salt users (IS-users) and 389 nonusers (IS-nonusers). Ultrasound (US) was performed to identify thyroid hypoechogenicity, suggestive of Hashimoto thyroiditis (HT). TgAb epitope pattern in 16 IS-users and 17 IS-nonusers was evaluated by an inhibition binding assay to Tg, using human monoclonal TgAb-Fab directed to A, B, C, and D epitopes on Tg.

RESULTS

Median urinary iodine excretion was slightly higher in IS-users than in IS-nonusers (112.0 μg/L vs 86.5 μg/L; P < .01). TgAb, and not TPOAb, was more frequent in IS-users (18.9% vs 13.6%, P = .02). HT-US was found in 87 subjects, among whom both positive TgAb (58.4% vs 31.8%, P = .03) and TPOAb (61.5% vs 45.4%. P = .04) were more frequent in IS-users. In this group significantly higher serum levels of TgAb (median 108 U/mL vs 30 U/mL; P = .02), but not of TPOAb, were present. Iodized salt use had no effect on the 1208 non HT-US subjects. TgAb directed to the epitope B of Tg were more frequent in IS-users than in IS-nonusers (27.5% vs 3.0%, P = .047).

CONCLUSIONS

Iodine-induced thyroid autoimmunity is related to TgAb and the unmasking of a cryptic epitope on Tg contributes to this relationship in humans.

Congenital hypothyroidism caused by a novel homozygous mutation in the thyroglobulin gene

Congenital hypothyroidism (CH) due to thyroglobulin (TG) deficit is an autosomal recessive disease (OMIM #274700) characterized by hypothyroidism, goiter, low serum TG, and a negative perchlorate discharge test. The aim of this study was to perform the genetic analysis of the TG gene in two sisters born from consanguineus parents and affected by CH and low serum TG levels. The index patient and her sister were identified at neonatal screening for CH and treated with L-thyroxine (L-T4). After discontinuation of L-T4 therapy, hypothyroidism was confirmed, serum TG was undetectable, and no organification defect after (123)I scintigraphy and perchlorate test was shown; thyroid ultrasound showed a eutopic gland of normal size. DNA was extracted from peripheral white blood cells of the two sisters and the father. All 48 exons of TG gene were amplified by polymerase chain reaction and subjected to direct sequencing. A novel homozygous point mutation in exon 10 of TG gene was identified in the patient and her sister. The mutation determined a stop codon at position 768 (R768X) resulting in an early truncated protein or in the complete absence of the protein. The father (euthyroid) was heterozygous carrier of the mutation.

CONCLUSION

Genetic analysis of TG gene was performed in two sisters affected by CH. A novel point mutation of the TG gene determining a stop codon at position 768 of the protein was identified. The early truncated nonfunctioning protein or the absence of the protein due to the premature degradation of abnormal mRNA may be responsible of the observed phenotype.

The effect of voluntary iodine prophylaxis in a small rural community: the Pescopagano survey 15 years later

CONTEXT

Iodine deficiency disorders are a major public health problem, and programs have been implemented to improve iodine nutrition.

OBJECTIVE

The objective of the study was to verify the effects of voluntary iodine prophylaxis in a small rural community (Pescopagano, Italy).

DESIGN

The design of the study was the evaluation of the prevalence of thyroid disorders 15 years after a previous survey conducted before iodine prophylaxis.

SETTING

The setting for this study was a general community survey.

PARTICIPANTS

One thousand one hundred forty-eight residents were examined in 2010 and 1411 in 1995.

RESULTS

In 2010, 757 of 1148 subjects (65.9%) routinely used iodized salt, urinary iodine excretion being significantly higher than in 1955 (median 98.0 μg/L, vs 55.0 μg/L, P < .0001). The prevalence of goiter was lower in 2010 than in 1995 (25.8% vs 46.1%, P < .0001), mainly due to the reduction of diffuse goiter (10.3% vs 34.0%, P < .0001). In 2010 vs 1995, thyroid autonomy in subjects younger than 45 years old (3 of 579, 0.5% vs 25 of 1010, 2.5% P = .004) and nonautoimmune hyperthyroidism in subjects older than 45 years old (8 of 569, 1.4% vs 18 of 401, 4.5%, P = .03) were less frequent. The prevalence of hypothyroidism was higher in 2010 vs 1995 (5.0% vs 2.8%, P = .005), mainly because of an increased frequency of subclinical hypothyroidism in subjects younger than 15 years old (7 of 83, 8.4% vs 0 of 419, 0.0%, P < .0001). Accordingly, serum thyroid autoantibodies (19.5% vs 12.6%; P < .0001) and Hashimoto's thyroiditis (14.5% vs 3.5%; P < .0001) were more frequent in 2010 than in 1995.

CONCLUSIONS

In the present work, the role of voluntary iodine prophylaxis was assessed in a small rural community relatively segregated, in which genetic and other environmental factors have not substantially changed between the 2 surveys. Iodine intake strongly affected the pattern of thyroid diseases, but the benefits of correcting iodine deficiency (decreased prevalence of goiter and thyroid autonomy in younger subjects and reduced frequency of nonautoimmune hyperthyroidism in older subjects) far outweighs the risk of development of thyroid autoimmunity and mild hypothyroidism in youngsters.

Thyroglobulin autoantibodies in patients with papillary thyroid carcinoma: comparison of different assays and evaluation of causes of discrepancies

CONTEXT

Thyroglobulin autoantibodies (TgAb) have been proposed as a surrogate marker of thyroglobulin in the follow-up of differentiated thyroid carcinoma. Commercially available TgAb assays are often discordant. We investigated the causes of discrepancy.

DESIGN

TgAb were measured by three noncompetitive immunometric assays and three competitive RIA in 72 patients with papillary thyroid carcinoma and associated lymphocytic thyroiditis (PTC-T), 105 with papillary thyroid carcinoma and no lymphocytic thyroiditis (PTC), 160 with Hashimoto's thyroiditis, and in 150 normal subjects. The results of the six assays were correlated. TgAb epitope pattern, evaluated by inhibition of serum TgAb binding to thyroglobulin by TgAb-Fab regions A, B, C, and D, were compared in sera which were positive in all six assays (concordant sera) and positive in only one to five assays (discordant sera) were compared. TgAb International Reference Preparation (IRP) was measured in 2007 and 2009.

RESULTS

The correlations of the six assays ranged from -0.01 to 0.93 and were higher in PTC-T and Hashimoto's thyroiditis than in PTC and normal subjects. Two uncorrelated components, one including the three immunometric assays, the other the three RIA, explained 40 and 37% of the total variance of the results of the six assays. The levels of inhibition were higher in concordant sera than in discordant sera by TgAb-Fab region B (27.0%, 21.2-34.0 vs. 6.0%, and 2.7-12.7%) and region C (30.5%, 21.3-37.7 vs. 4.0%, and 1.0-6.5%); thus, the epitope pattern was more homogeneous in concordant sera than in discordant sera. TgAb IRP ranged from 157 to 1088 (expected 1000) IU/ml in 2009; results in 2007 were similar in all but two assays.

CONCLUSIONS

TgAb assays are highly discordant. Discrepancy is lower when comparing assays with similar methodology. Results of TgAb from PTC-T are more concordant than those from PTC because their epitope pattern is more restricted. The internal standardization of TgAb is generally, but not completely, satisfactory.

Thyroglobulin autoantibodies of patients with subacute thyroiditis are restricted to a major B cell epitope

BACKGROUND

Thyroglobulin autoantibodies (TgAb) can develop in patients with subacute thyroiditis (SAT).

AIM

Comparison of the epitope pattern of TgAb of patients with SAT, Hashimoto's thyroiditis (HT) [autoimmune thyroid disease (AITD)] and non-toxic multinodular goiter (NTMG) (non-AITD).

SUBJECTS AND METHODS

Serum TgAb from 10 patients with SAT, 45 with HT, and 19 with NTMG were evaluated. Serum TgAb binding to Tg was inhibited by 4 recombinant human TgAb-Fab, recognizing Tg epitope regions A, B, C, and D. The ability of single TgAb-Fab to inhibit the binding of serum TgAb to Tg was evaluated in enzymelinked immunosorbent assay.

RESULTS

Levels of inhibition were different for all TgAb-Fab in the 3 groups of patients. Inhibition by region A TgAb-Fab in SAT [50.5 (30.3-62.5)%] (median and 25th to 75th percentiles) was similar to HT [49.0 (38.0-69.5)%] and significantly higher than in NTMG [25.0 (14.0-37.0)%]; by region B TgAb-Fab in SAT [0.0 (0.0-12.5)%] was significantly lower than in HT [28.0 (9.5-48.0)%] and similar to NTMG [9.0 (4.8-20.5)%]; by region C TgAb-Fab in SAT [9.5 (0.0-25.8)%] were similar to HT [23.0 (9.5-41)%] and NTMG [6.5 (1.7-21.5)%]; and by region D TgAb-Fab in SAT [0.0 (0.0-8.0)%] were lower than in HT [12.0 (1.0-28.5)%] and similar to NTMG [1.0 (0.0-5.0)%].

CONCLUSIONS

The epitope pattern of TgAb of SAT is restricted to the A region that is immunodominant in AITD and non-AITD. In the majority of patients with SAT, the autoimmune phenomena represent a non-specific and transient response to the release of thyroid antigens, rather than the expression of thyroid autoimmunity.

Lymphocytic thyroiditis on histology correlates with serum thyroglobulin autoantibodies in patients with papillary thyroid carcinoma: impact on detection of serum thyroglobulin

CONTEXT

Serum thyroglobulin (Tg), the marker of residual tumor in papillary thyroid carcinoma, can be underestimated in patients with Tg autoantibodies (TgAb). TgAb are due to a coexistent lymphocytic thyroiditis (LT) or the papillary thyroid carcinoma per se. TgAb assays are highly discordant.

DESIGN

We evaluated 141 patients with a clinical diagnosis of nodular thyroid disease, 32 of Hashimoto's thyroiditis, and four of Graves' disease, who underwent total thyroidectomy for an associated papillary thyroid carcinoma. Patients were classified as papillary thyroid carcinoma-lymphocytic thyroiditis (PTC-T) and papillary thyroid carcinoma (PTC) according to the presence or absence of LT on histology. Tg was measured before thyroid remnant ablation, when it is expectedly detectable, by an immunometric assay (IMA) and TgAb by three noncompetitive IMA and three competitive radioimmunoassays (RIA). The number of lymphocytes was compared with TgAb concentration.

RESULTS

Seventy-two of 177 patients (40.7%) were classified as PTC-T and 105 (59.3%) as PTC. Although the tumor stage was similar in the two groups, Tg was undetectable in more PTC-T (37 of 72) than PTC (12 of 105) (P < 0.01), and Tg values were lower in the former (0; 0-4.7 ng/ml) (median; 25th to 75th percentiles) than in the latter group (9.7; 2.7-24.2) (P < 0.01). Accordingly, the percent of positive TgAb by the six assays resulted in higher PTC-T (29.2-50.0%) than PTC (1.9-6.7%) (P < 0.01). Among 49 patients with undetectable Tg, TgAb were more frequently positive by IMA (57.1-63.3%) than RIA (30.6-42.9%). The number of lymphocytes correlated with TgAb concentration in all six assays (0.34 < Rho < 0.46) (all P < 0.01).

CONCLUSIONS

In papillary thyroid carcinoma, LT on histology must be carefully searched for because it is frequently associated with TgAb and therefore mistakenly low or undetectable Tg. TgAb can be missed by some assays. In absence of LT, TgAb are rare.

Identification and functional analysis of novel dual oxidase 2 (DUOX2) mutations in children with congenital or subclinical hypothyroidism

CONTEXT

Congenital hypothyroidism (CH) associated with goiter or a gland of normal size has been linked to dual oxidase 2 (DUOX2) mutations in the presence of iodide organification defect.

OBJECTIVE

Thirty unrelated children with CH or subclinical hypothyroidism (SH) identified during infancy with a eutopic thyroid gland, coming from our Screening Centre for CH or referred from other regions of Italy, were studied with the perchlorate discharge test to identify organification defects. Eleven children with iodide organification defect were considered for the genetic analysis of TPO, DUOX2, and dual oxidase maturation factor 2 (DUOXA2) genes.

PATIENTS

Eight children with CH and three with SH and eutopic thyroid gland were included in the study. After discontinuation of therapy, a partial or complete organification defect was shown after ¹²³I scintigraphy and perchlorate test.

METHODS

TPO, DUOX2, and DUOXA2 genes were analyzed, and functional activity of DUOX2 variants was studied in HeLa cells.

RESULTS

Sequencing of the DUOX2 gene revealed a deletion S965fsX994 in three children; two were euthyroid after 1 month of L-T₄ discontinuation but developed SH after 5 and 18 months, respectively, whereas the other child had SH. One child with SH showed H678R, R701Q, and P982A substitutions, and another child with SH showed only the P982A. One child with SH showed the Y1150C mutation, and another euthyroid child showed the A728T mutation. Functional studies confirmed that S965fsX994, Y1150C, and A728T mutations were responsible for the defect in H₂O₂ production, whereas H678R, R701Q, and P982A did not alter H₂O₂ production in vitro.

CONCLUSIONS

Genetic analysis of the DUOX2 gene was performed in 11 children with organification defect. Two new mutations (Y1150C and A728T) and the deletion S965FsX994 were responsible for the deficit in the organification process and the phenotypes. Three polymorphisms (H678R, P982A, and R701Q) were identified.

Genetics and phenomics of hypothyroidism and thyroid dys- and agenesis due to PAX8 and TTF1 mutations

Thyroid dysgenesis (TD) is the most common cause of congenital hypothyroidism (CH), a relatively frequent endocrine disease in newborns (1 in 3000-4000 live births). TD is a defect in the organogenesis of the gland resulting in hypoplastic, ectopic or absent-thyroid gland. TD is usually sporadic but mutations in transcription factors (PAX8, TTF1, FOXE1 and NKX2-5) involved in thyroid development have been shown to cause a minority of cases transmitted as Mendelian diseases. This review focuses on the genetics and phenomics of hypothyroidism and TD due to PAX8 and TTF1 mutations.

Congenital hypothyroidism and late-onset goiter: identification and characterization of a novel mutation in the sodium/iodide symporter of the proband and family members

BACKGROUND

Iodide transport defects (ITDs), rare causes of congenital hypothyroidism (CH), have been shown to arise from abnormalities of the sodium/iodide symporter (NIS). We describe a 16-year-old girl with CH caused by an ITD resulting from a novel mutation of NIS.

SUMMARY

A 16-year-old girl with CH diagnosed by a neonatal screening program received early treatment with L-thyroxine replacement therapy. A (123)I scan had failed to reveal any iodide uptake by the thyroid and salivary glands; thus, thyroid agenesis was diagnosed. Thyroglobulin (Tg) was not measured when she was a neonate or infant. Unexpectedly, at the age of 14.5 years, a nodular goiter and high serum Tg concentrations (303 ng/mL; normal, <50) were identified. Her thyroid radioactive iodine uptake was very low as was the saliva to plasma iodide ratio (0.5). Analysis of her NIS gene revealed an in-frame six-nucleotide deletion of the coding sequence (1206-1211delGTCGGC) corresponding to the deletion of amino acids 287 and 288 of the human NIS protein located at the beginning of the VIII transmembrane segment. The proband was homozygous for this deletion, whereas both unrelated parents and her brother were heterozygous. COS-7 cells transfected with the mutant NIS failed to concentrate iodide, confirming that the mutation was the direct cause of the ITD in this patient.

CONCLUSIONS

We describe a patient with CH caused by a previously not described mutation of the NIS gene that was inherited from her parents. We therefore recommend that thyroid ultrasonography be performed in CH patients with low radioactive iodine uptake and elevated serum Tg.

Identification and functional studies of two new dual-oxidase 2 (DUOX2) mutations in a child with congenital hypothyroidism and a eutopic normal-size thyroid gland

CONTEXT

Some cases of congenital hypothyroidism (CH) are associated with a gland of normal size.

OBJECTIVE

To explore the cause of organification defect in one child with CH and a eutopic thyroid gland, genetic analyses of TPO, DUOX2, and DUOXA2 genes were performed.

PATIENT

One child with CH, a eutopic thyroid gland, and a partial organification defect was shown after (123)I scintigraphy and perchlorate test.

METHODS

In the child with the organification defect, TPO, DUOX2, and DUOXA2 genes were analyzed. The functional activity of the DUOX2 mutants was studied after expression in eukaryotic cells.

RESULTS

No TPO or DUOXA2 gene mutations were identified. Direct sequencing of the DUOX2 gene revealed a compound heterozygous genotype for S911L and C1052Y substitutions. S911L and C1052Y caused a partial defect in H(2)O(2) production after transient expression in HeLa cells.

CONCLUSIONS

We performed a genetic analysis in one child with CH and a eutopic thyroid gland. Two new mutations in DUOX2 gene responsible for the partial deficit in the organification process were identified.

Loss-of-function mutations in the thyrotropin receptor gene as a major determinant of hyperthyrotropinemia in a consanguineous community

CONTEXT

Resistance to TSH (RTSH) is a condition of impaired responsiveness of the thyroid gland to TSH, characterized by elevated serum TSH, low or normal thyroid hormone levels, and hypoplastic or normal-sized thyroid gland.

OBJECTIVES

The aim of the study was to evaluate the clinical course and the genotype-phenotype relationship of RTSH caused by two different TSH receptor (TSHR) gene mutations in a consanguineous population.

PATIENTS AND METHODS

We conducted a clinical and genetic investigation of 46 members of an extended family and 163 individuals living in the same town. In vitro functional studies of the mutant TSHRs were also performed.

RESULTS

Two TSHR gene mutations (P68S and L653V) were identified in 33 subjects occurring as homozygous L653V (five subjects), heterozygous L653V (20 subjects), heterozygous P68S (four subjects), and compound heterozygous L653V/P68S (four subjects). With the exception of one individual with concomitant autoimmune thyroid disease, all homozygotes and compound heterozygotes presented with compensated RTSH (high TSH with free T(4) and T(3) in the normal range). Only nine of 24 heterozygotes had mild hyperthyrotropinemia. The L653V mutation resulted in a higher serum TSH concentration and showed a more severe in vitro abnormality than P68S. Haplotype analysis predicted a founder of the L653V six to seven generations earlier, whereas the P68S is older. Cross-sectional and prospective longitudinal studies indicate that TSH and T(4) concentrations remain stable over time.

CONCLUSIONS

High frequency hyperthyrotropinemia in an Israeli Arab-Muslim consanguineous community is attributed to two inactivating TSHR gene mutations. Concordant genotype-phenotype was demonstrated clinically and by in vitro functional analysis. Retrospective and prospective studies indicate that in the absence of concomitant autoimmune thyroid disease, elevated TSH levels reflect stable compensated RTSH.

Identification of TSH receptor mutations in three families with resistance to TSH

OBJECTIVE

Genetic analysis of the TSH receptor gene in seven subjects with subclinical hypothyroidism (SH), in whom the diagnosis of autoimmune thyroid disease had been excluded by laboratory and instrumental techniques currently available.

PATIENTS

Three families where different members (2 children and 5 adults) affected by SH were studied. GENETIC ANALYSIS: Genomic DNA was extracted from peripheral lymphocytes and the entire coding sequence of the TSHr gene was sequenced. pSVL-TSHr construct harbouring a Q8fsX62 insertion was obtained by site-directed mutagenesis. COS-7 cells transfected with wild-type and mutant receptor were used for binding studies, flow cytometry, and cyclic AMP (cAMP) determination.

RESULTS

A four base pair (bp) duplication in position 41 (41TGCAins), leading to a premature stop of translation at codon 62 (Q8fsX62), was found to be heterozygous in the proband, the father and the sister in Family 1. In Family 2 the proband and the sister were heterozygous for the mutation D410N. In Family 3 the proband and the father were heterozygous for the mutation P162A. After transfection in COS-7 cells, the mutant receptor Q8fsX62 displayed a low expression at the cell surface, and a reduced response to bovine TSH (bTSH) in terms of cAMP production.

CONCLUSIONS

We identified TSH receptor mutations in seven members of three families with subclinical hypothyroidism.

Pituitary-thyroid setpoint and thyrotropin receptor expression in consomic rats

The genetic basis for differences in TSH sensitivity between two rat strains was examined using consomic rats generated from original strains salt-sensitive Dahl (SS) (TSH 1.8 +/- 0.1 ng/ml; free T(4) index 4.9 +/- 0.4) and Brown Norwegian (BN) (TSH 5.5 +/- 0.6 ng/ml, P < 0.05; free T(4) index 4.3 +/- 0.1, P not significant). Consomic rats SSBN6 [BN chromosome (CH) 6 placed in SS rat] and SSBN2 (BN CH 2 placed in SS rat) have TSH concentrations intermediate between pure SS and BN strains (2.9 +/- 0.3 and 3.1 +/- 0.3 ng/ml, respectively; P < 0.05). Candidate genes on rat CH 2 included TSH beta-subunit and on CH 6 the TSH receptor (TSHR). TSH from sera of BN, SS, SSBN6, and SSBN2 strains had similar in vitro bioactivity suggesting that the cause for the variable TSH concentrations was not due to an altered TSH. Physiological response to TSH was measured by changes in serum T(4) concentrations upon administration of bovine TSH (bTSH). Rat strain SS had a greater T(4) response to bTSH than BN (change in T(4), 1.3 +/- 0.1 vs. 0.4 +/- 0.1 microg/dl, P < 0.005), suggesting reduced thyrocyte sensitivity to TSH in BN. Sequencing of the TSHR coding region revealed an amino acid difference in BN (Q46R). This substitution is unlikely to contribute to the strain difference in serum TSH because both TSHR variants were equally expressed at the cell surface of transfected cells and responsive to bTSH. Given similar TSH activity and similar TSHR structure, TSHR mRNA expression in thyroid tissue was quantitated by real-time PCR. BN had 54 +/- 5% the total TSHR expression compared to SS (100 +/- 7%, P < 0.0001), when corrected for GAPDH expression, a difference confirmed at the protein level. Therefore, the higher TSH level in the BN strain appears to reflect an adjustment of the feedback loop to reduced thyrocyte sensitivity to TSH secondary to reduced TSHR expression. These strains of rat provide a model to study the cis- and trans-acting factors underlying the difference in TSHR expression.

Genetic analysis of the PAX8 gene in children with congenital hypothyroidism and dysgenetic or eutopic thyroid glands: identification of a novel sequence variant

OBJECTIVE

To analyse the coding region of PAX8 in individuals with congenital (CH) or post neonatal hypothyroidism due to dysgenetic (TD) or eutopic thyroid glands.

DESIGN AND PATIENTS

Forty-three children with CH and TD (13 agenesis, 23 ectopia, and seven hypoplasia), one subject with post neonatal onset of hypothyroidism and thyroid ectopia, 15 children with CH and eutopic thyroid glands and six euthyroid adults with thyroid hemiagenesis were enrolled as cases, along with 120 healthy individuals as controls.

MEASUREMENTS

Exons 2-8 of the PAX8 were directly sequenced. HeLa and HEK293 cells were transfected with PAX8 wild-type (PAX8-WT), mutant PAX8, p300, thyroid transcription factor 1 (TTF-1) and thyroglobulin promoter pGL3 (TG prom-pGL3). Synergism of TTF-1 with PAX8-WT vs. mutant and activity of PAX8-WT vs. mutant in accompaniment with p300 on TG prom-pGL3 were also assessed. The luminescence produced by PAX8-WT and mutant PAX8 was measured.

RESULTS

Among patients and controls only a 15-year-old girl with thyroid ectopia showed a heterozygous transition of cytosine to thymine at position 674 in exon 6, which changed a conserved threonine at position 225 to methionine (PAX8-T225M). Her father and sister harboured PAX8-T225M without abnormal thyroid phenotypes. PAX8-T225M and PAX8-WT similarly increased luciferase activity and had a similar synergistic effect with TTF-1. At 500 ng p300, however, PAX8-T225M could not significantly increase TG promoter activity when compared to PAX8-T225M alone, while PAX8-WT +500 ng p300 induction was significantly higher than PAX8-WT alone (P < 0.001). Cotransfection of TTF-1 together with PAX8-T225M resulted in rescuing of the lack of synergism with p300.

CONCLUSIONS

PAX8 mutations in congenital hypothyroidism due to dysgenetic or orthotopic thyroid glands are rare. PAX8-T225M is probably a rare variant.

Repulsive Separation of the Cytoplasmic Ends of Transmembrane Helices 3 and 6 Is Linked to Receptor Activation in a Novel Thyrotropin Receptor Mutant (M626I)

Ligand-dependent activation of G protein-coupled receptors (GPCRs) involves repositioning of the juxtacytoplasmic ends of transmembrane helices TM3 and TM6. This concept, inferred from site-directed spin labeling studies, is supported by chemical cross-linking of the cytoplasmic ends of TM3 and TM6 blocking GPCR activation. Here we report a novel constitutive active mutation (M626I) in TM6 of the TSH receptor (TSHR), identified in affected members of a family with nonautoimmune hyperthyroidism. The specific constitutive activity of M626I, measured by its basal cAMP generation corrected for cell surface expression, was 13-fold higher than that of wild-type TSHR. Homology modeling of the TSHR serpentine domain based on the rhodopsin crystal structure suggests that M626 faces the side chain of I515 of TM3 near the membrane-cytoplasmic junction. Steric hindrance of the introduced isoleucine by I515 is consistent with the fact that shorter or more flexible side chains at position 626 did not increase constitutivity. Furthermore, a reciprocal mutation at position 515 (I515M), when introduced into the M626I background, acts as revertant mutation by allowing accommodation of the isoleucine sidechain at position 626 and fully restoring the constitutive activity to the level of wild-type TSHR. Thus, repulsive separation of the juxtacytoplasmic TM6 and TM3 in the M626I model conclusively demonstrates a direct link between the opening of this cytoplasmic face of the receptor structure and G protein coupling.

Presence and absence of follicle-stimulating hormone receptor mutations provide some insights into spontaneous ovarian hyperstimulation syndrome physiopathology

CONTEXT

Ovarian hyperstimulation syndrome (OHSS) is a potentially life-threatening complication of ovarian stimulation treatments. Moreover, four mutations of the FSH receptor (FSHr) were recently described in patients presenting with spontaneous OHSS (sOHSS) of the first trimester of pregnancy with normal levels of human chorionic gonadotropin (hCG).

OBJECTIVE

The objective of this study was to look for novel FSHr mutations in patients with sOHSS associated with different levels of hCG and TSH to 1) find new residues important for FSHr activation and specificity, and 2) better delineate the pathophysiology of the different presentations of sOHSS. DESIGN, INTERVENTION, AND PATIENTS: After blood sampling, we sequenced the FSHr from genomic leukocytes DNA from eight patients with sOHSS of the first or second trimester of pregnancy with normal or high hCG levels or with high TSH levels associated with severe hypothyroidism.

SETTING

This study was performed at a university laboratory.

MAIN OUTCOME MEASURE

The main outcome measure was FSHr sequencing and in vitro evaluation of the variation of cAMP production of FSHr mutants.

RESULTS

A new mutation was found in the patient with sOHSS of the first trimester of pregnancy with a normal hCG level: I5.54(545)T, in transmembrane helix V of the FSHr. When tested functionally, this mutant displayed promiscuous activation by both hCG and TSH together with detectable constitutive activity. In contrast, no mutations were found in the FSHr from patients with high hCG or TSH levels, indicating that for those seven patients, sOHSS results from the natural promiscuous stimulation of a wild-type FSHr by very high concentrations of hCG or TSH.

CONCLUSIONS

sOHSS can occur by at least three different pathophysiological mechanisms.

Glycoprotein hormone receptors: link between receptor homodimerization and negative cooperativity

The monomeric model of rhodopsin-like G protein-coupled receptors (GPCRs) has progressively yielded the floor to the concept of GPCRs being oligo(di)mers, but the functional correlates of dimerization remain unclear. In this report, dimers of glycoprotein hormone receptors were demonstrated in living cells, with a combination of biophysical (bioluminescence resonance energy transfer and homogenous time resolved fluorescence/fluorescence resonance energy transfer), functional and biochemical approaches. Thyrotropin (TSHr) and lutropin (LH/CGr) receptors form homo- and heterodimers, via interactions involving primarily their heptahelical domains. The large hormone-binding ectodomains were dispensable for dimerization but modulated protomer interaction. Dimerization was not affected by agonist binding. Observed functional complementation indicates that TSHr dimers may function as a single functional unit. Finally, heterologous binding-competition studies, performed with heterodimers between TSHr and LH/CG-TSHr chimeras, demonstrated the unsuspected existence of strong negative cooperativity of hormone binding. Tracer desorption experiments indicated an allosteric behavior in TSHr and, to a lesser extent, in LH/CGr and FSHr homodimers. This study is the first report of homodimerization associated with negative cooperativity in rhodopsin-like GPCRs. As such, it may warrant revisitation of allosterism in the whole GPCR family.

Genetic analysis of TTF-2 gene in children with congenital hypothyroidism and cleft palate, congenital hypothyroidism, or isolated cleft palate

Homozygous null mice for thyroid transcription factor (TTF)-2 gene exhibit cleft palate and thyroid malformation. We performed a genetic analysis of the TTF-2 gene in 2 children with congenital hypothyroidism (CH) and cleft palate, 45 children with thyroid dysgenesis, 19 children with isolated cleft palate or cleft lip, 4 patients with thyroid hemiagenesis. The entire coding-region of the TTF-2 gene was analyzed by direct sequencing. Direct sequencing of the TTF-2 gene revealed polymorphisms in the length of the polyalanine tract. The most frequent stretch length was 14 residues and it was found in 50 of 70 (71%) and in 45 of 53 (85%) normal healthy controls. A polyalanine tract of 16 residues in the heterozygous state was seen in 18 of 70 (26%) cases and in 4 of 53 (7%) normal subjects. In 1 of 4 (25%) case of hemiagenesis a polyalanine tract of 16 residues in the homozygous state was observed. In 1 of 26 agenesis the polyalanine tract consisted of 12 residues in the heterozygous state. Direct sequencing also revealed the presence of two silent polymorphisms. No mutations were identified in the TTF-2 gene. In conclusion, our results show that no genetic alteration was present in the TTF-2 gene of these patients, suggesting that defects in the TTF-2 gene are a rare event.

Modulation of ligand selectivity associated with activation of the transmembrane region of the human follitropin receptor

Recently, three naturally occurring mutations in the serpentine region of the FSH receptor (FSHr) (D567N and T449I/A) have been identified in three families with spontaneous ovarian hyperstimulation syndrome (OHSS). All mutant receptors displayed abnormally high sensitivity to human chorionic gonadotropin and, in addition, D567N and T449A displayed concomitant increase in sensitivity to TSH and detectable constitutive activity. In the present study, we have used a combination of site-directed mutagenesis experiments and molecular modeling to explore the mechanisms responsible for the phenotype of the three OHSS FSHr mutants. Our results suggest that all mutations lead to weakening of interhelical locks between transmembrane helix (TM)-VI and TM-III, or TM-VI and TM-VII, which contributes to maintaining the receptor in the inactive state. They also indicate that broadening of the functional specificity of the mutant FSHr constructs is correlated to their increase in constitutive activity. This relation between basal activity and functional specificity is a characteristic of the FSHr, which is not shared by the other glycoprotein hormone receptors. It leads to the interesting suggestion that different pathways have been followed during primate evolution to avoid promiscuous stimulation of the TSHr and FSHr by human chorionic gonadotropin. In the hFSHr, specificity would be exerted both by the ectodomain and the serpentine portion.

A mutation in the follicle-stimulating hormone receptor as a cause of familial spontaneous ovarian hyperstimulation syndrome

Ovarian hyperstimulation syndrome (OHSS) occurs mainly after excessive stimulation of the ovaries by exogenous gonadotropins administrated in the context of in vitro fertilization procedures (iatrogenic OHSS). Recently, spontaneous and recurrent occurrence of the disease (spontaneous OHSS) was shown in two families to be caused by mutations affecting the follitropin receptor (FSHr). The two mutant FSHr (T449I, D567N) harbor aminoacid substitutions in the serpentine portion of the receptor and display abnormally high sensitivity to the pregnancy hormone hCG, thus providing a satisfactory explanation to the phenotype. In addition, mutant D567N showed also increased sensitivity to thyrotopin (TSH) and displayed increase in basal (ligand-independent) activity. In this report, we describe a new familial case of recurrent OHSS. The affected women were heterozygous for a different mutation involving codon 449, where an alanine was substituted for threonine. Similar to D567N, the T449A FSHr mutant shows an increase of its sensitivity to both hCG and TSH, together with an increase in basal activity. Together with the two previous studies, this report shows that inappropriate stimulation of the FSHr by hCG is a cause of spontaneous OHSS.

A mutation in the follicle-stimulating hormone receptor as a cause of familial spontaneous ovarian hyperstimulation syndrome

Ovarian hyperstimulation syndrome (OHSS) occurs mainly after excessive stimulation of the ovaries by exogenous gonadotropins administrated in the context of in vitro fertilization procedures (iatrogenic OHSS). Recently, spontaneous and recurrent occurrence of the disease (spontaneous OHSS) was shown in two families to be caused by mutations affecting the follitropin receptor (FSHr). The two mutant FSHr (T449I, D567N) harbor aminoacid substitutions in the serpentine portion of the receptor and display abnormally high sensitivity to the pregnancy hormone hCG, thus providing a satisfactory explanation to the phenotype. In addition, mutant D567N showed also increased sensitivity to thyrotopin (TSH) and displayed increase in basal (ligand-independent) activity. In this report, we describe a new familial case of recurrent OHSS. The affected women were heterozygous for a different mutation involving codon 449, where an alanine was substituted for threonine. Similar to D567N, the T449A FSHr mutant shows an increase of its sensitivity to both hCG and TSH, together with an increase in basal activity. Together with the two previous studies, this report shows that inappropriate stimulation of the FSHr by hCG is a cause of spontaneous OHSS.

TSH receptor and Gs(alpha) genetic analysis in children with Down's syndrome and subclinical hypothyroidism

The prevalence of thyroid diseases in children with Down's syndrome (DS) is about 3%. The most frequently observed condition is autoimmune subclinical hypothyroidism (SH). Autoimmune SH must be distinguished from defects in the biological activity of the TSH molecule or from the rare inherited condition of thyroid resistance to TSH. To investigate this last aspect we studied 12 patients with DS that had moderately elevated TSH with normal free thyroid hormones without signs of autoimmunity. For the genetic analysis the genomic DNA was extracted from peripheral lymphocytes. All the exons of the TSH receptor (TSHr) and Gs(alpha) genes were sequenced. The genetic analysis of the TSHr gene revealed the presence of four polymorphic variants. In two patients there was an allelic variant in the exon 1 (Pro52Thr--in one patient in the heterozygous state and in the other as a homozygous substitution). In one patient there was an allelic variant in the exon 1 (Asp36His) in the heterozygous state. In 11 patients there was a silent polymorphism in the exon 7 at nucleotide 561. All patients were homozygous for a silent polymorphism in the exon 9 at nucleotide 855. No inactivating mutations of TSHr or Gs(alpha) genes were identified in the 12 patients. In conclusion, our results seem to exclude the role of TSHr or Gs(alpha) gene mutations in the pathogenesis of the non-autoimmune SH observed in some children with DS.

Role for inner ring deiodination preventing transcutaneous passage of thyroxine

Creams containing thyroid hormone are commonly employed for cosmetic purposes. To verify whether T(4) applied to the skin surface can enter the bloodstream either directly or as a metabolite, a cream containing L-T(4) [3,5,3',5'-tetraiodothyronine (T(4))] was self-applied by volunteers for 2 wk. No significant variations in urinary iodide, TSH, and serum (total and free) T(4) and T(3) concentrations were observed at any time relative to pretreatment values, whereas rT(3) concentrations increased significantly 6 and 12 h after cream application. The increased rT(3) concentration led us to investigate the presence of inner ring type III deiodinase (D3) activity in human skin. Using human surgical discard skin, we found that T(4) can be carried across human epidermis in a liposome cream. Substantial inner ring deiodination was suggested by the fact that only 10% of transferred thyroid hormone remained as T(4), and T(3) was not detected. We then measured D3 activity in a surgical skin specimen. The K(m) for T(3) was 1.74 nmol/liter, and the maximum velocity was 23.5 fmol/microg microsomal protein/h. In conclusion, our study indicates that normal human skin serves as a substantial, but incomplete, barrier to T(4) passage. D3 plays an important role in augmenting T(4) blockade by inactivating T(4) to rT(3).

Cytotoxic effects of carboplatinum and epirubicin in the setting of an elevated serum thyrotropin for advanced poorly differentiated thyroid cancer

Chemotherapy represents the only therapeutic option in most poorly differentiated thyroid carcinomas, although its effect is limited and short lasting. The aim of this study was to evaluate whether increasing the metabolic rate of thyroid cancer cells by TSH stimulation might result in higher response rate to chemotherapy. Fourteen patients with poorly differentiated thyroid carcinoma and nonfunctioning diffuse lung metastases detected at computed tomography scan, entered this study. A combination of carboplatinum and epirubicin was administered at 4- to 6-wk intervals for six courses. TSH stimulation was achieved by reduction of the daily dose of L-thyroxine resulting in mild hypothyroidism (eight patients) or by administration of recombinant human TSH (six patients). Two additional patients did not complete the therapeutic protocol due to severe hematological side effects. Results were evaluated by comparison of lung computed tomography scans before and after therapy. One patient had a complete remission. Five patients had partial remission, and seven patients had disease stabilization. One patient progressed to death. The overall rate of positive responses was 37% that rose to 81% when including patients with stable disease. Serum thyroglobulin after chemotherapy declined more than 50% in six patients, with respect to basal levels. Apparently, no difference in the response rate was observed between exogenous or endogenous TSH stimulation. At the time of this analysis, among the patients who completed the treatment courses, 9 of 14 patients (64.3%) are still alive (median survival from start of chemotherapy = 21 months, range: 15-34). Six of these patients did not show progression of lung disease, whereas regrowth of lung metastases was observed in three patients after 19, 20, and 21 months from chemotherapy, respectively. Five patients died of their disease, including the one who had progression of lung disease during chemotherapy, three who died for brain or bone metastases, and one who died for refractory local tumor invasion. No progression of lung metastases was observed until death in these four patients. In conclusion, the response rate of poorly differentiated thyroid cancer to chemotherapy observed in this study was favorable and promising. TSH stimulation may have contributed to these results.

Evidence for a role of the type III-iodothyronine deiodinase in the regulation of 3,5,3'-triiodothyronine content in the human central nervous system

OBJECTIVE

Thyroid hormone is essential for maintaining normal neurological functions both during development and in adult life. Type III-iodothyronine deiodinase (D3) degrades thyroid hormones by converting thyroxine and 3,5,3'-triiodothyroinine (T3) to inactive metabolites. A regional expression of D3 activity has been observed in the human central nervous system (CNS), and a critical role for D3 has been suggested in the regulation of local T3 content in concert with other enzymes.

DESIGN

This study was undertaken to further characterize D3 activity in human CNS and to understand its role in the local regulation of T3 content.

METHODS

Autoptic specimens from various areas of human CNS were obtained 6--27 h postmortem from 14 donors who died from cardiovascular accident, neoplastic disease or infectious disease. D3 was determined by measuring the conversion of T3 to 3,3'-diiodothyronine. The T3 content was measured by radioimmunoassay in ethanol extracts, using a specific antiserum.

RESULTS

High levels of D3 activity were observed in hippocampus and temporal cortex, lower levels being found in the thalamus, hypothalamus, midbrain cerebellum, parietal and frontal cortex, and brain stem. An inverse relationship between D3 activity and T3 content in these areas was demonstrated.

CONCLUSIONS

We have concluded that D3 contributes to the local regulation of T3 content in the human CNS.

Neuropsychological follow-up in early-treated congenital hypothyroidism: a problem-oriented approach

Screening programs for congenital hypothyroidism (CH) dramatically improved the neuropsychological prognosis in affected children. However, mild impairments in cognitive performances, poorer motor skills, defective language abilities, and learning problems have been reported in some studies of early-treated CH children. The occurrence of these defects makes neuropsychological follow-up mandatory. The aim of the present study was to identify those neuropsychological functions that are more frequently affected in early-treated CH children and that might require prompt rehabilitation treatment to prevent permanent defects. The study group involved 24 CH children. Levothyroxine (LT4) treatment (initial dose 8-10 microg/kg per day) was started at mean age of 28 days (range 15-45) and was then adjusted with the goal to keep thyrotropin (TSH) and free thyroid hormone levels in the normal range. Cognitive evaluation was performed at 3, 5, and 7 years of age and did not significantly differ from that of controls. Mean neurological scores were lower in children 5 years of age than in controls. Children with severe neonatal hypothyroidism (serum thyroxine [T4] < 2 microg/dL) had significantly lower neurological scores compared to less affected CH children and normal controls. The most affected functions were balance, extremity coordination, fine motricity, quality of movements, associated movements, and head movements. Language disorders were observed in half of CH children at 3 and 5 years of age, but moderately severe defects were restricted to those with severe neonatal hypothyroidism. In conclusion, a problem-oriented, simplified neuropsychological follow-up of early-treated children with CH should not systematically include the frequent repetition of time-consuming and expensive psychometric tests because individual IQ scores are in the normal range of tests in almost all CH children and can be differentiated from those of normal controls only on a population-statistic basis. Selected tests of motor proficiency are indicated at 3 and 5 years of age to detect those defects in motor skills that appear to be more specifically affected in CH children. Language performances are at particular risk in CH children, and should be always checked at 3 and 5 years of age. Children with even mild language disorders or delayed language achievements should be regularly reevaluated at 6-month intervals and, if no spontaneous improvement is observed, they should receive specific rehabilitation treatment. No further motor and language evaluation is warranted in CH children with normal tests at age 5 years.

School attainments in children with congenital hypothyroidism detected by neonatal screening and treated early in life

OBJECTIVE

Evaluation of school attainments in children with congenital hypothyroidism (CH) detected by neonatal screening and treated early in life.

PATIENTS AND METHODS

Text comprehension, mathematics, reading, writing and verbal and spatial memory, as indices of school learning, were evaluated in nineteen 5- to 10-year-old children with CH attending nursery or elementary school. l-Thyroxine substitution (starting dose 8-10 microg/kg body weight per day) was initiated at a mean age of 30+/-10 days of life. The control group included 298 unaffected children matched with the CH children for age and school grade. Thirty per cent of controls were classmates of CH children. Intelligence quotients (IQ), language performances and motor development were evaluated in CH children at age 5 years, and were related to their school attainments. School performances of CH children were also compared with their neonatal serum thyroxine (T4) concentration, and with the social-cultural level of the family.

RESULTS

Four out of 19 (21%) children with CH, 3 in the nursery and 1 in the elementary school, displayed a generalized learning disorder. Symbol copy, geometric copy, phrase repetition, dictation writing and spontaneous writing were particularly defective in nursery school CH children, while orthographic error recognition was defective in elementary school CH children. School learning disorders in CH children were significantly correlated with a borderline-low IQ, poor language performances and a low social-cultural level of the family, but not with motor skills or neonatal T4 concentration.

CONCLUSION

School attainments of early treated CH children were within the normal range in most affected cases. However, about 20% of CH children, most of them attending nursery school, showed a generalized learning disorder. Low IQ scores and poor language performances at age 5 years were associated with defective learning, mainly in CH children living in a poor social-cultural environment. In this subset of CH children, prompt initiation of speech and psychomotor rehabilitation therapy is recommended in order to prevent subsequent school learning disorders.

[Transient congenital hypothyroidism: physiopathology and clinica]

The fetus and the newborn are more sensitive than adults to a reduced environmental iodine supply, and in iodine-deficient areas, transient neonatal hypothyroidism is frequently observed. This transient thyroid failure may be associated with neonatal goiter and elevated serum thyroglobulin levels at birth. Borderline elevated neonatal serum TSH concentrations frequently occur in newborns in iodine deficient areas, and result in a higher recalling rate at the screening for congenital hypothyroidism. Minor defects in mental performances and neurological development are observed in children living in areas of mild to moderate iodine deficiency, and result from the concomitant effects of iodine deficiency in the mother during pregnancy and transient neonatal hypothyroidism. Endemic cretinism is the severe and irreversible neurological consequence of iodine deficiency during fetal and neonatal life. Iodine prophylaxis is highly effective in preventing the development of iodine deficiency disorders including transient neonatal hypothyroidism. Since iodine prophylaxis in Italy is inadequate, variable degrees of iodine deficiency are still present all-over the country, and are responsible of a higher incidence of transient neonatal hypothyroidism or hyperthyrotropinemia.

Serum iodothyronines in the human fetus and the newborn: evidence for an important role of placenta in fetal thyroid hormone homeostasis

The pattern of circulating iodothyronines in the fetus differs from that in the adult, being characterized by low levels of serum T3. In this study, concentrations of various iodothyronines were measured in sera from neonates of various postconceptional age (PA). Results obtained in cord sera at birth (PA, 24-40 weeks), reflecting the fetal pattern, were compared with those found during extrauterine life in newborns of 5 days or more of postnatal life (PA, 27-46 weeks). The main findings are: Starting at 30 weeks of PA, serum levels increase linearly during extrauterine life; and at 40 weeks, they are more than 200% of those measured in cord sera from newborns of equivalent PA. Serum reverse T3 (rT3) levels during fetal life are higher than those measured during extrauterine life; but they significantly decrease, starting at 30 weeks of PA. Serum T3 sulfate (T3S) does not significantly differ between the two groups, showing the highest values at 28-30 weeks of PA, and significantly decreasing at 30-40 weeks. T3S levels are directly correlated with rT3, both in fetal and extrauterine life, whereas a significant negative correlation between T3S and T3 is found only during extrauterine life.

IN CONCLUSION

1) changes in serum concentrations of iodothyronines in umbilical cord and during postnatal life indicate that maturation of extrathyroidal type I-iodothyronine monodeiodinase (MD) accelerates, starting at 30 weeks of PA; 2) high levels of type III-MD activity in fetal tissues prevent the rise of serum T3, whereas they maintain high levels of rT3 during intrauterine life; 3) an important mechanism leading to the transition from the fetal to the postnatal thyroid hormone balance is a sudden decrease in type III-MD activity; iv) because placenta contains a high amount of type III-MD, it is conceivable that placenta contributes to maintain low T3 and high rT3 serum concentrations during fetal life and that its removal at birth is responsible for most changes in iodothyronine metabolism occurring afterwards.

Chronic recurrent stress due to panic disorder does not precipitate Graves' disease

A role of psychic stress in precipitating hyperthyroid Graves' disease has been suggested, but the evidence in support of this pathogenetic mechanism is conflicting. In this study we investigated the possible occurrence of Graves' disease in patients with panic disorder, a psychiatric condition characterized by recurrent endogenous stress. The study group included 87 consecutive patients suffering from panic disorder since 1 to 30 years: 17 males (mean age 31.3, range 26-43 years) and 70 females (mean age 37.6, range 15-73 years). Two hundred and sixty-two normal subjects with no present or past history of psychiatric disorder served as controls. Patients were submitted to a full evaluation of the thyroid that included physical examination, assays for free thyroid hormones, TSH, thyroglobulin (TgAb), thyroperoxidase (TPOAb) and TSH receptor (TRAb) antibodies, and thyroid echography. The prevalence of circulating TgAb and/or TPOAb in patients with panic disorder did not differ from that in the control group. Twelve patients with panic disorder (13.7%) had circulating TgAb and/or TPOAb, but none had TRAb. Three out of 12 patients with thyroid antibodies, indicating a genetic susceptibility to autoimmune thyroid disease, had a family history of clinical thyroid autoimmunity, and 4 of them had a hypoechogenic pattern of the thyroid at ultrasound suggesting autoimmune thyroiditis. None of the patients with panic disorder had a previous history of hyperthyroidism. On examination, clinical hyperthyroidism or endocrine ophthalmopathy were not found in any of them. A small goiter was appreciated by palpation in 16 patients (18.3%). Free thyroid hormones and TSH were within the normal range in all patients but one: a 55-year old lady with normal serum free thyroid hormones and undetectable TSH. During an 18-month follow-up she did not develop hyperthyroidism and her TSH spontaneously returned in the normal range. Considering the individual duration of panic disorder, evidence for previous or present Graves' hyperthyroidism was not found for a total of 478 patient-years of exposure to recurrent endogenous stress in the whole study group, and for a total of 39 patient-years in patients with a genetic susceptibility to autoimmune thyroid disease. In conclusion, we found that recurrent endogenous stress did not precipitate Graves' hyperthyroidism in a series of 87 patients with panic disorder, encompassing a total of 478 patient-years of exposure to stress. Failure to activate the hypothalamic-pituitary-adrenal axis by endogenous stress due to panic disorder as opposed to exogenous stress due to life-events might explain why panic disorder does not precipitate Graves' hyperthyroidism.

Neuropsychological development in a child with early-treated congenital hypothyroidism as compared with her unaffected identical twin

OBJECTIVE

Neonatal screening for congenital hypothyroidism (CH) prevents the serious neuropsychological features of CH, but the question remains whether intelligence and motor skills of CH children treated early are completely normal.

DESIGN

In this report we describe the rare case of two genetically identical twins, only one of whom was affected by CH due to thyroid agenesis. L-Thyroxine (9 microg/kg body weight/day) therapy was initiated at 27 days of age and was adequate throughout the follow-up.

METHODS

Neuropsychological evaluation was performed on the twins in parallel from 3 months to 8 years of age.

RESULTS

The CH twin (NB) did not show major neuromotor impairments but, compared with the unaffected twin (EB), she had a slight delay in postural/motor achievements and in language development that completely disappeared at 8 years of age. On standardised tests of intelligence, NB was indistinguishable from control children but, compared with her twin, she had lower IQ scores in most testing occasions up to 7 years of age (NB = 108 vs EB = 115). School achievements of NB did not significantly differ from those of her classmates but, compared with her twin, she scored worse in writing, mechanical reading, verbal memory, and possibly in arithmetic.

CONCLUSIONS

Because the twins were genetically and phenotypically identical, were raised in the same environment, and received a similar education, it is concluded that hypothyroidism in utero and in the first neonatal month was responsible for the lower neuropsychological achievements of the CH twin. While foetal hypothyroidism is at present unavoidable, earlier diagnosis and initiation of treatment in neonates with CH are important and highly recommended.