Subclinical hypothyroidism in children and adolescents: a wide range of clinical, biochemical, and genetic factors involved

Overt Hypothyroidism and Severe Growth Retardation in a Preschool Girl with Poorly Controlled Nephrotic Syndrome: Case Report and Literature Review

Background

Nephrotic children may develop thyroid hormone dysfunction due to urinary excretion of thyroid hormones. In contrast to the subclinical hypothyroidism that affects around 30% of children with nephrotic syndrome (NS), the patient in this case had overt hypothyroidism and severe growth retardation.

Clinical case

A 5 years and 8 months old girl with steroid-dependent NS was referred from another center due to persistent edema and decreased diuresis, being treated with mycophenolate mofetil (MMF) 250 mg once a day and L-thyroxine 50 mcg daily since 4 months of NS onset because of hypothyroidism. Her albumin was 12.64 g/l, cholesterol 25.64 mmol/l and proteinuria 5 g/l. Severe growth retardation was observed: patient's height was 93.5 cm (-13 cm <3 percentile), weighted 17.2 kg (15-25 percentile). Her disease vintage was over 3 years. Girl's growth velocity has slowed down from 3.5 months. The patient received a high cumulative dose of prednisolone (approx. 7800 mg in 1 year and 8 months). Thyroid-stimulating hormone was higher (18.04 mU/L) with reduced FT4 11.43 pmol/l and IGF-1 < 15 µg/L. Kidney biopsy revealed minimal change disease, and genetic testing was negative. Intensive NS treatment with methylprednisolone pulse therapy, enlarged doses of MMF and albumin infusion were started and L-thyroxine dose was increased to 75 mcg. TPOAb was in normal range (12.65 IU/ml). After 3 weeks she was discharged with no edema and after stopping methylprednisolone treatment thyroid function normalized and L-thyroxin was discontinued. Two weeks later standard growth hormone stimulation test with clonidine showed partially insufficient growth hormone secretion. During NS remission with normalization of thyroid function (TSH 6.680 mU/l, FT4 13.85 pmol/l) and normalization of IGF-1 level (132 mcg/l) partial catch-up growth was observed (height velocity increased from 3.5 cm/year to 7.3 cm/year, based on 4-month calculation period).

Conclusions

Clinicians should be aware of a risk of developing hypothyroidism and consider thyroid function testing during the treatment of children with NS, as well as actively treat hypothyroidism and evaluate growth.

[Pathogenic TSHR variants in children with thyroid dysgenesis]

BACKGROUND

Loss-of-function mutations in the TSH receptor gene (TSHR) (NP_000360.2) are the potential causes of thyroid dysgenesis in patients with congenital hypothyroidism. Heterozygous variants of the TSHR gene lead to partial resistance to TSH, homozygous and compound heterozygous variants have been shown to cause CH due to thyroid hypoplasia or TSH resistance. Recently more and more articles in this field have appeared in the international literature sources, while local publications are limited. The studies are necessary to understand the etiology, pathogenesis of the disease, to improve the management of these patients.

AIM

To assess the frequency of incidence of pathogenic variants of the TSHR gene in children with CH due to thyroid dysgenesis. To study inheritance and phenotypic patterns of CH in families.

MATERIALS AND METHODS

In this single-center interventional one-stage non-comparative study a group of CH patients was examined. The patients underwent neck ultrasound and radionuclide imaging. The examination was performed 14 days after hormone replacement therapy suspension or prior to its initiation. The structure of thyroid dysgenesis was estimated, genetic testing for mutations in the TSHR gene was performed using the NGS method.

RESULTS

The study included 95 children with primary CH (75 girls; 20 boys). The patients' median age at the time of examination was 6.2 years [4.5; 8.9], the median level of neonatal TSH was 157.5 mU/l [60.9; 257.2]. Ectopic thyroid was found in 52% of children, aplasia in 36%, hypoplasia and hemiagenesis in 10% and 2%, respectively. In 5.4% of cases (in 5 out of 95 patients), different variants of the TSH gene were detected. Two children had heterozygous p.R450H and p.D487N variants in TSHR gene, two patients was homozygous for the p.S49Afs * 9 variant, one child had compound heterozygous variants (p.A485D and p.R450H). According to ultrasound imaging, all patients had thyroid hypoplasia of varying severity. Three children underwent thyroid scintigraphy, which revealed decreased 99mТc pertechnetate uptake (0.3-0.9%).

CONCLUSION

In our study, the incidence of different variants in the TSHR gene in children with CH was 5.3%. Our analysis uncovered two previously undescribed variants. Genetic testing may be able to help with making the diagnosis, patient's management, and genetic counseling.

Emotional intelligence scores in children and adolescents with subclinical hypothyroidism-correlation with serum serotonin and thyroid-stimulating hormone (TSH) concentrations

INTRODUCTION

Thyroxine is essential for nervous system development. Subclinical hypothyroidism (SCH), also known as mild thyroid failure, is associated with impaired cognitive function in children and mood disorders in adults. Serotonin is also involved in brain development as well as in mood and behavior modulation. The possible interaction between thyroid function tests, serum serotonin concentrations, and emotional intelligence (EI) was studied.

METHODS

A total of 224 schoolchildren from the Peloponnese, Greece, aged 11-19, were included in the study, of whom 26.3% had SCH. Emotional quotients (EQ), such as well-being, self-control, emotionality, and sociability, were assessed using the TEIQue-ASF questionnaire, and TSH, fT4, and serum serotonin concentrations were also evaluated.

RESULTS

Children and adolescents with SCH had a lower EQ total score (p < 0.001), EQ well-being score (p = 0.025), EQ self-control score (p = 0.029), EQ emotionality score (p = 0.029), and EQ sociability score (p = 0.010) and lower serum serotonin concentrations (p < 0.001).

CONCLUSIONS

Children and adolescents with SCH exhibited lower EI scores and lower serum serotonin concentrations when compared with age-matched healthy controls.

Thyroid Volume and Thyroid Function Parameters Are Independently Associated with Weight Status in Overweight Children

BACKGROUND

A relation between thyroid-stimulating hormone (TSH), insulin resistance - both of which are related to obesity - and thyroid volume has been suggested. Therefore, we analyzed thyroid volume and structure in relation to thyroid function parameters, weight status, and insulin resistance.

METHODS

This is a cross-sectional study in which weight status (BMI-SDS), thyroid function parameters (TSH, free tri-iodothyronine [fT3], and free thyroxine [fT4]), insulin resistance index (HOMA-IR), and thyroid volume (ultrasound) were determined in 617 overweight children (aged 10.4 ± 2.2 years, 50% male, BMI-SDS 2.5 ± 0.6) and in 27 normal-weight children of a similar age and gender. Furthermore, changes in thyroid volume and structure, and thyroid function parameters were analyzed in 83 obese children (51% male, mean age 10.3 ± 2.2) at baseline and at the end of a 1-year lifestyle intervention.

RESULTS

Overweight children had a significant greater thyroid volume (4.2 ± 1.8 vs. 4.1 ± 0.5 mL) and higher TSH (3.1 ± 1.5 vs. 2.4 ± 1.1 mU/L) and fT3 (4.4 ± 0.7 vs. 4.1 ± 0.5 pg/mL) concentrations compared to normal-weight children. In multiple linear regression analyses adjusted to multiple confounders, thyroid volume was significantly related to BMI-SDS (b coefficient 0.44 ± 0.10, r2 = 0.41) but not to any thyroid function parameter or HOMA-IR. Changes in BMI-SDS were significantly associated with changes in thyroid volume (r = 0.22). The changes in thyroid volume were not correlated to changes of any thyroid function parameter or HOMA-IR.

CONCLUSIONS

Thyroid volume is positively correlated to weight status in childhood obesity and the change is reversible after weight loss independently of thyroid function parameters and insulin resistance. Further studies are needed to understand why thyroid volume is increased reversibly in overweight children.

Thyroid function in patients with idiopathic nephrotic syndrome

BACKGROUND

Albumin is the major protein excreted in urine in patients with nephrotic syndrome (NS). However, low-molecular-weight proteins including some binding proteins are also excreted. Thyroid hormone and its binding globulins are excreted in urine in excess in nephrotic syndrome. Therefore, it has been postulated that patients with nephrotic syndrome may show hypothyroidism, subclinical or overt.

METHODS

In this prospective observational study, patients of idiopathic nephrotic syndrome aged 1-40 years of both gender were included. Serum T3, T4 and TSH were assayed at diagnosis and repeated at 12 weeks or at remission whichever was earlier. Renal biopsy was performed as required.

RESULTS

Among 100 patients taken for analysis (42 children, 58 adult), 30 cases were of first episode, 40 were of frequent relapse/steroid-dependent NS, and 30 patients had steroid-resistant NS (SRNS). Three (3%) cases had overt hypothyroidism and 18 (18%) patients had subclinical hypothyroidism. Most hypothyroid cases belonged to SRNS subgroup. Mean Serum T3, T4 and TSH values showed significant improvement in remission in comparison to nephrosis state (P < 0.01). Serum TSH had significant positive correlation (r = 0.391, P < 0.01) with 24-h proteinuria and negative correlation with serum albumin (r =  - 0.303, P < 0.01) in nephrosis.

CONCLUSION

Hypothyroidism is common among nephrotic syndrome patients especially in SRNS subgroup. Therefore, routine screening is recommended in steroid-resistant nephrotic syndrome patients.

Thyroid Dysfunction in Children with Idiopathic Nephrotic Syndrome Attending a Paediatric Hospital in Qazvin, Iran

Objectives

Nephrotic syndrome is a glomerular disease characterised by a loss of albumin and high-molecular-weight proteins such as thyroxine-binding globulin and thyroid hormones, potentially resulting in subclinical or even overt hypothyroidism. This study aimed to compare thyroid hormone levels between nephrotic children and healthy controls as well as between nephrotic children in the active phase of the disease and those in remission.

Methods

This case-control study was conducted between March 2016 and 2018 at a paediatric hospital in Qazvin, Iran. A total of 73 nephrotic children comprised the case group—including 49 with active disease and 24 in remission—while the control group included 74 healthy children. Thyroid function was assessed according to levels of thyroid-stimulating hormone (TSH), free triiodothyronine (T3), free thyroxine (T4), total T4, total T3 and anti-thyroid peroxidase.

Results

All of the controls had normal total T4 levels. Elevated TSH levels were more frequent in nephrotic children compared to controls (34.2% versus 10.8%; P = 0.001). A significantly lower number of patients with active disease were euthyroid compared to those in remission (51% versus 95.8%; P = 0.001). Moreover, 7 (9.5%) of patients in the active and no patient in remission phase had abnormal total T4 levels (P <0.001), while 14.3% and 0% had highly elevated TSH levels (P = 0.002).

Conclusion

Due to the prevalence of subclinical and even overt hypothyroidism, thyroid screening tests may be required for nephrotic children. However, further research is needed to confirm these findings.

TSH promotes adiposity by inhibiting the browning of white fat

Adiposity is caused by an imbalance between energy intake and consumption. Promotion of the browning of white fat increases energy expenditure and could combat adiposity. Thyroid-stimulating hormone (TSH) has been confirmed to positively correlate with adiposity. However, the putative connection between TSH and white adipose browning has never been explored. In this study, we sought to assess the effect of TSH on white adipose tissue browning and energy metabolism. Subclinical hypothyroidism mice, thyroid-specific Tshr-knockout mice injected with TSH, adipocyte-specific and global Tshr-knockout micewere subjected to morphological, physiological, genetic or protein expression analyses and metabolic cages to determine the role of TSH on the browning of white adipose tissue and metabolism. 3T3-L1 and primary SVF cells were used to verify the effects and mechanism of TSH on the browning of white adipocytes. We show that increased circulation TSH level decreases energy expenditure, promotes adiposity, impairs glucose and lipid metabolism. Knockout of Tshr decreases adiposity, increases energy expenditureand markedly promotes the development of beige adipocytesin both epididymal and inguinal subcutaneous white fat via a mechanism that likely involves AMPK/PRDM16/PGC1α. Our results reveal an important role of TSH in regulating energy balance and adiposity by inhibiting the browning of white fat.

Subclinical hypothyroidism in childhood, treatment or only follow-up?

Background

Subclinical hypothyroidism (SH) is defined as serum levels of thyroid-stimulating hormone (TSH) above the upper limit with normal concentrations of free T4 (fT4). Its management remains challenging. The aim of the study was to evaluate clinical and laboratory findings as well as the clinical course of children with SH followed in a third level hospital. Sixty-five patients aged between 2 and 18 years old were retrospectively studied.

Methods

The patients were followed for a median period of 9 months (range 6 months to 24 months). Those who normalized TSH levels were discharged (Group 1). If TSH persisted mildly elevated (5-10μUI/mL) with normal fT4 and negative TPOAb/TgAb, they were classified as Group 2 and followed semi-annually without treatment. Those patients whose TSH raised ≥10μUI/mL or who maintained TSH 5-10μUI/mL and positive TPOAb/TgAb were considered suitable for thyroxin therapy (Group 3, G3).

Results

In 89% of our patients, TSH concentrations spontaneously reverted to normality or remained stable without treatment (Groups 1 and 2), whereas less than 11% progressed to clinical hypothyroidism (Group 3). Baseline TSH was significantly lower in group 1 than in group 3. In group 3 the prevalence of female sex (71%) was higher and TPO antibodies were present in 85% of patients. The risk of developing overt hypothyroidism in patients with positive anti-thyroid antibodies respect to those who normalized TSH was 45 (95%CI 6.5–312.5).

Conclusion

Baseline TSH, female sex and the presence of thyroid autoimmunity were the best predictors of the evolution to SH over time.

Importance of thyroid-stimulating hormone levels in liver disease

Objectives Recently, several studies have reported the association between elevation of thyroid-stimulating hormone (TSH) levels and liver disease, especially, non-alcoholic fatty liver disease (NAFLD). We aimed to evaluate the incidence and risk factors of TSH elevation in patients with liver disease. Methods We retrospectively reviewed the data of patients aged <18 years who were diagnosed with liver disease between January 2015 and March 2019. Results Among the 77 patients, 17 (22.1%) had subclinical hypothyroidism and 3 (17.6%) progressed to overt hypothyroidism. A total of 26 (33.8%) patients had NAFLD, and 6 (23.1%) had subclinical hypothyroidism. The ultrasound grade of liver steatosis was not related to the elevation of TSH levels. The median age was significantly younger in patients with TSH elevation (5 vs. 9 years, p = 0.017). Albumin levels were significantly decreased (3.9 vs. 4.3 g/dL, p = 0.007), and total bilirubin levels were elevated (2.2 vs. 0.6 mg/dL, p = 0.001) in patients with subclinical hypothyroidism. Conclusions TSH elevation commonly occurs in patients with liver disease, especially those with younger age. The cause of liver disease was not a risk factor for TSH elevation.

ASSOCIATIONS OF THYROID VOLUME AND FUNCTION WITH CHILDHOOD OBESITY

Context

The links between obesity and thyroid function or thyroid volume in children are still controversial with limited available data.

Objective

This study aimed to examine thyroid function and volume in obese Turkish school-age children in comparison to normal-weight children.

Design

Cross-sectional study.

Subjects and Methods

One hundred obese children (47 boys, 53 girls; mean age 10.34±2.79 years) with a body mass index (BMI) above 95th percentile, and 100 normal-weight children (42 boys, 58 girls; 10.34±2.79 years) were included. The study parameters were BMI z score (Z-BMI), body surface area (BSA), thyroid volume, free thyroxine (fT4) and thyroid stimulating hormone (TSH) levels.

Results

The mean TSH and fT4 levels did not show a significant difference between obese and normal-weight children (p>0.05). The mean thyroid volume was higher in obese children (6.46±5.84 and 4.64±1.44, respectively; p=0.043). fT4 correlated negatively with Z-BMI in both normal-weight and obese children (r=-0.285, p=0.004 and r=-0.289, p=0.004, respectively). Thyroid volume, on the other hand, correlated positively with Z-BMI, again in both normal-weight and obese children (r=0.657, p<0.001 and r=0.444, p<0.001, respectively). Similar associations were found for BSA.

Conclusions

Thyroid volume correlated positively and fT4 correlated negatively with Z-BMI and BSA, in both obese and normal-weight school-age children, whereas TSH appears to be independent of these parameters.

Mild Hypothyroidism in Childhood: Who, When, and How Should Be Treated?

Mild hypothyroidism, also known as subclinical hypothyroidism (SH), is biochemically defined as serum TSH levels above the upper limit of the reference range, in the presence of normal serum concentrations of total T4 and free T4 (FT4). In the neonatal period, mild hypothyroidism can be defined by the presence of a TSH value between 6 and 20 mIU/L and normal FT4 levels. After the neonatal period, SH can be defined mild if TSH ranges between 4.5 and 10 mIU/L. The management of mild hypothyroidism in childhood is challenging. The major concern is to establish whether this condition should always be considered an expression of mild thyroid dysfunction. Indeed, the effects of untreated mild hypothyroidism are still not completely defined. In the neonatal period, concern exists about neurocognitive outcome; in children, although there is no clear evidence of alterations in growth or neurocognitive development, subtle cardiovascular abnormalities have been documented. Therefore, there is still uncertainty about the need of treatment across all ages, and the management should be based on the age of the child, the etiology, and the degree of TSH elevation, as well as on other patient factors. This review updates current evidences on diagnosis and management of mild hypothyroidism in childhood.

Generation and characterization of a hypothyroidism rat model with truncated thyroid stimulating hormone receptor

Thyroid stimulating hormone receptor (TSHR), a G-protein-coupled receptor, is important for thyroid development and growth. In several cases, frameshift and/or nonsense mutations in TSHR were found in the patients with congenital hypothyroidism (CH), however they have not been functionally studied in an animal model. In the present work, we generated a unique Tshr^Df/Df rat model that recapitulates the phenotypes in TSHR Y444X patient by CRISPR/Cas genome editing technology. In this rat model, TSHR is truncated at the second transmembrane domain, leading to CH phenotypes as what was observed in the patients, including dwarf, thyroid aplasia, infertility, TSH resistant as well as low serum thyroid hormone levels. The phenotypes can be reversed, at least partially, by levothyroxine (L-T4) treatment after weaning. The thyroid development is severely impaired in the Tshr^Df/Df rats due to the suppression of the thyroid specific genes, i.e., thyroperoxidase (Tpo), thyroglobulin (Tg) and sodium iodide symporter (Nis), at both mRNA and protein levels. In conclusion, the Tshr^Df/Df rat serves as a brand new genetic model to study CH in human, and will greatly help to shed light into the development of terminal organs that are sensitive to thyroid hormones.

Association between monoallelic TSHR mutations and congenital hypothyroidism: a statistical approach

OBJECTIVE

Biallelic TSHR mutations cause congenital hypothyroidism (CH). Serum TSH levels of monoallelic mutation carriers range from normal to mildly elevated, and thus the size of its effect remains unclear. The objectives were to examine the association between monoallelic TSHR mutations and positivity at newborn screening (NBS) for CH, and to test whether the association was modified by another genetic factor.

SUBJECTS AND METHODS

We enrolled 395 patients that had a positive result in NBS and sequenced TSHR. Monoallelic TSHR mutation carriers were further sequenced for DUOX2. Molecular functions of the mutations were verified in vitro. The frequency of the mutations in the study subjects was compared with a theoretical value in the Japanese general population. Odds ratio (OR) for NBS positivity associated with the mutation was calculated. Using Bayes' theorem, we estimated a posterior probability of NBS positivity given the mutation.

RESULTS

Twenty-six monoallelic TSHR mutation carriers were found. Four out of the 26 also had a monoallelic DUOX2 mutation (double heterozygotes). The frequencies of monoallelic TSHR mutation carriers (6.6%) and double heterozygotes (1.0%) were significantly higher than those in the general population (0.58% and 0.0087%, respectively). OR for NBS positivity of having a monoallelic TSHR mutation or being a double heterozygote was 12.0 or 117.9, respectively. Posterior probability of NBS positivity was 0.38% in monoallelic TSHR mutation carriers and 3.8% in double heterozygotes.

CONCLUSIONS

Monoallelic TSHR mutations are significantly associated with NBS positivity, and the association is further strengthened by the coexistence of monoallelic DUOX2 mutations.

Non-Autoimmune Subclinical and Overt Hypothyroidism in Idiopathic Steroid-resistant Nephrotic Syndrome in Children

OBJECTIVE

To evaluate the frequency of non-autoimmune subclinical and overt hypothyroidism in children with idiopathic steroid-resistant nephrotic syndrome (SRNS).

METHODS

This cross-sectional study recruited 30 children (age 1-18 y) with idiopathic SRNS; and 30 healthy controls. Serum T3, T4 and TSH were performed in cases as well as controls. Anti-thyroid peroxidase and anti-thyroglobulin antibody tests were performed in all cases.

RESULTS

Non-autoimmune subclinical or overt hypothyroidism was detected in 10 out of 30 children with idiopathic SRNS; 2 had overt hypothyroidism, while 8 patients had subclinical hypothyroidism. Children with SRNS had a mean (SD) TSH value 4.55 (4.64) mIU/L that was higher as compared to controls (1.88 (1.04) mIU/L) (P<0.01). Focal segmental glomerulosclerosis (FSGS) was the commonest histopathological condition, seen in 13 (43.3%). Children with overt hypothyroidism (2 cases) and grade III subclinical hypothyroidism (1 case) were subsequently started on levothyroxine therapy.

CONCLUSION

The prevalence of subclinical and overt hypothyroidism seems to be high in idiopathic SRNS, with almost one-third of children having overt or subclinical non-autoimmune hypothyroidism.

The debate on treating subclinical hypothyroidism

Subclinical hypothyroidism (SCH) represents a mild or compensated form of primary hypothyroidism. The diagnosis of SCH is controversial, as its symptoms are non-specific and its biochemical diagnosis is arbitrary. The treatment of SCH was examined among non-pregnant adults, pregnant adults and children. In non-pregnant adults, treatment of SCH may prevent its progression to overt hypothyroidism, reduce the occurrence of coronary heart disease, and improve neuropsychiatric and musculoskeletal symptoms associated with hypothyroidism. These benefits are counteracted by cardiovascular, neuropsychiatric and musculoskeletal side effects. SCH is associated with adverse maternal and fetal outcomes that may improve with treatment. Treating SCH in children is safe and may improve growth. Importantly, the evidence in this field is largely from retrospective and prospective studies with design limitations, which precludes a conclusive recommendation for the treatment of SCH.

Endocrinological Evaluations of a Neurofibromatosis Type 1 Cohort: Is it Necessary to Evaluate Autoimmune Thyroiditis in Neurofibromatosis Type 1?

Background:

Neurofibromatosis type 1 is an autosomal dominant neurocutaneous disorder in which the coexistence of autoimmune thyroiditis and thyroid gland tumours has been reported previously.

Aims:

To determine the thyroid function and autoimmune thyroid diseases in neurofibromatosis type 1 patients in order to identify the possible association between neurofibromatosis type 1 and thyroid diseases.

Study Design:

Case-control study.

Methods:

The study includes 78 consecutive patients diagnosed with neurofibromatosis type 1 between June 2010 and June 2014 and 50 healthy controls. Baseline demographic data were generated from patient examination record forms, including age, sex, height, and weight, as well as levels of free triiodothyronine, free thyroxine, thyroid-stimulating hormone, anti-thyroid peroxidase and anti-thyroglobulin levels.

Results:

Mean age, sex, and body mass index were similar in both groups (p>0.05). The mean levels of free triiodothyronine, free thyroxine, and thyroid-stimulating hormone were not statistically different between the neurofibromatosis type 1 and control groups. Similarly, no statistically significant difference was observed between the neurofibromatosis type 1 and control groups for anti-thyroid peroxidase and anti-thyroglobulin positivity (2.5% vs 0%, p>0.05).

Conclusion:

Screening for autoimmune thyroid disease and thyroid function seems to be unnecessary in patients with neurofibromatosis type 1.

Thyroid function in children and adolescents with Hashimoto's thyroiditis after l-thyroxine discontinuation

OBJECTIVE

Thyroid function may recover in patients with Hashimoto's thyroiditis (HT).

DESIGN

To investigate thyroid function and the need to resume l-thyroxine treatment after its discontinuation.

SETTING

Nine Italian pediatric endocrinology centers.

PATIENTS

148 children and adolescents (25 m and 123 f) with HT on treatment with l-thyroxine for at least one year.

INTERVENTION AND MAIN OUTCOME MEASURE

Treatment was discontinued in all patients, and serum TSH and fT4 concentrations were measured at the time of treatment discontinuation and then after 2, 6, 12 and 24 months. Therapy with l-thyroxine was re-instituted when TSH rose >10 U/L and/or fT4 was below the normal range. The patients were followed up when TSH concentrations were between 5 and 10 U/L and fT4 was in the normal range.

RESULTS

At baseline, TSH was in the normal range in 139 patients, and was between 5 and 10 U/L in 9 patients. Treatment was re-instituted after 2 months in 37 (25.5%) patients, after 6 months in 13 patients (6.99%), after 12 months in 12 patients (8.6%), and after 24 months in an additional 3 patients (3.1%). At 24 months, 34 patients (34.3%) still required no treatment. TSH concentration >10 U/L at the time of diagnosis was the only predictive factor for the deterioration of thyroid function after l-thyroxine discontinuation.

CONCLUSIONS

This study confirms that not all children with HT need life-long therapy with l-thyroxine, and the discontinuation of treatment in patients with a TSH level <10 U/L at the time of diagnosis should be considered.

Disorders of thyroid morphogenesis

Developmental anomalies of the thyroid gland, defined as thyroid dysgenesis, underlie the majority of cases of congenital hypothyroidism. Thyroid dysgenesis is predominantly a sporadic disorder although a reported familial enrichment, variation of incidence by ethnicity and the monogenic defects associated mainly with athyreosis or orthotopic thyroid hypoplasia, suggest a genetic contribution. Of note, the most common developmental anomaly, thyroid ectopy, remains unexplained. Ectopy may result from multiple genetic or epigenetic variants in the germline and/or at the somatic level. This review provides a brief overview of the monogenic defects in candidate genes that have been identified so far and of the syndromes which are known to be associated with thyroid dysgenesis.

Resistance to thyrotropin

Resistance to thyrotropin (RTSH) is broadly defined as reduced sensitivity of thyroid follicle cells to stimulation by biologically active TSH due to genetic defects. Affected individuals have elevated serum TSH in the absence of goiter, with the severity ranging from nongoitrous isolated hyperthyrotropinemia to severe congenital hypothyroidism with thyroid hypoplasia. Conceptually, defects leading to RTSH impair both aspects of TSH-mediated action, namely thyroid hormone synthesis and gland growth. These include inactivating mutations in the genes encoding the TSH receptor and the PAX8 transcription factor. A common third cause has been genetically mapped to a locus on chromosome 15, but the underlying pathophysiology has not yet been elucidated. This review provides a succinct overview of currently defined causes of nonsyndromic RTSH, their differential diagnoses (autoimmune; partial iodine organification defects; syndromic forms of RTSH) and implications for the clinical approach to patients with RTSH.

Unfavorable Course of Subclinical Hypothyroidism in Children with Hashimoto's Thyroiditis Compared to Those with Isolated Non-Autoimmune Hyperthyrotropinemia

Subclinical hypothyroidism (SCH) is a common problem in pediatric population, and the natural history of SCH varies depending on its etiology. Whether Hashimoto's thyroiditis (HT) negatively affects the natural course of SCH was investigated in pediatric patients without concomitant diseases. Predictors for levothyroxine medication were also evaluated. Medical records of 109 children with SCH (91 girls, 5?18 years) diagnosed between 2005 and 2014 were retrospectively reviewed. Patients were classified into HT (n = 37) and isolated non-autoimmune hyperthyrotropinemia (iso-NAHT, n = 72). During median 2 years of follow-up, only 10.1% of SCH patients eventually initiated levothyroxine, and HT patients showed a higher probability of requiring levothyroxine medication than iso-NAHT patients (21.6% vs. 4.2%). Underlying HT independently predicted deterioration of thyroid function, leading to levothyroxine medication (hazard ratios [HRs], 4.6 vs. iso-NAHT, P = 0.025). High titers of anti-thyroglobulin antibodies (TGAbs) predicted later medication in the HT group (HRs, 28.2 vs. normal TGAbs, P = 0.013). Most pediatric SCH showed benign and self-remitting courses. Underlying HT significantly increases the risk for levothyroxine medication, especially with high titers of TGAbs.

Subclinical hypothyroidism in childhood - current knowledge and open issues

Subclinical hypothyroidism is defined as serum levels of TSH above the upper limit of the reference range, in the presence of normal concentrations of total T₄ or free T₄. This biochemical profile might be an indication of mild hypothyroidism, with a potential increased risk of metabolic abnormalities and cardiovascular disease recorded among adults. Whether subclinical hypothyroidism results in adverse health outcomes among children is a matter of debate and so management of this condition remains challenging. Mild forms of untreated subclinical hypothyroidism do not seem to be associated with impairments in growth, bone health or neurocognitive outcome. However, ongoing scientific investigations have highlighted the presence of subtle proatherogenic abnormalities among children with modest elevations in their TSH levels. Although current findings are insufficient to recommend levothyroxine treatment for all children with mild asymptomatic forms of subclinical hypothyroidism, they highlight the potential need for assessment of cardiovascular risk among children with this condition. Increased understanding of the early metabolic risk factors associated with subclinical hypothyroidism in childhood will help to improve the management of affected individuals.

Next-generation sequencing analysis of TSHR in 384 Chinese subclinical congenital hypothyroidism (CH) and CH patients

BACKGROUND

Defects in the human TSHR gene are reported to be one of the causes of CH due to thyroid dysgenesis, the purpose of this study was to examine the TSHR mutation spectrum and prevalence in congenital hypothyroidism (CH) and subclinical congenital hypothyroidism (SCH) patients in the Guangxi Zhuang Autonomous Region of China and to evaluate the genotype-phenotype correlations.

METHODS

Blood samples were collected from 384 patients including 240 CH and 144 SCH patients in Guangxi, China. Genomic DNA was extracted from peripheral blood leukocytes. All exons of the 11 known CH associated genes including TSHR together with their exon-intron boundaries were screened by next-generation sequencing (NGS).

RESULTS

NGS analysis of TSHR revealed nine different variants in ten individuals. Six (4.2%) of 144 patients with SCH were found to harbor monoallelic TSHR variants. Four (1.6%) of 240 patients with CH harbored TSHR variants combined with another monoallelic mutation in either DUOX2 or TG gene. The present study identified five novel variants c.1838A>G (p.Y613C), c.1576G>A (p.A526T), c.2087T>G (p.F696C), c.1631G>A (p.G544E) and c.2051C>A (p.A684D) in TSHR, seven known pathogenic variants c.1349G>A (p.R450H), c.326G>A (p.R109Q), c.2066T>G (p.V689G) and c.2272G>A (p.E758K) in TSHR, IVS3+2T>G in TG, and c.1588A>T (p.K530X) and c.2635G>A (p.E879K) in DUOX2. The previously reported hotspot mutation p.R450H was found in only one SCH patient.

CONCLUSION

The prevalence of TSHR mutations was 1.6% in CH patients and 4.2% in SCH patients in Guangxi Zhuang Autonomous Region of China. Monoallelic TSHR pathogenic variants were associated with SCH, while TSHR pathogenic variants combined with monoallelic mutations in DUOX2 or TG gene might contribute to CH. Our study expands the TSHR mutation spectrum and provides the best estimation of mutation rate for SCH and CH patients in this Chinese population.

High prevalence of DUOX2 gene mutations among children with congenital hypothyroidism in central China

Congenial hypothyroidism (CH) is the most common congenital endocrine disease and is treatable when recognized early enough. We investigated the genetic variants in 12 children diagnosed with CH by newborn screening in Huangshi area central China. Twelve genes commonly involved in CH development were studied. Genomic DNA from peripheral blood was used to amplify all exons of the selected genes, and the constructed sequencing libraries were subjected to next generation high throughput DNA sequencing (NGS). Analysis of the sequencing results identified rare genetic variants in 11 of the 12 patients (91.7%), and two novel rare variants were found in DUOX2 gene and two in TPO gene. Mutations in DUOX2 gene were identified in 10 patients (83.3%), and all these patients were found to carry bi-allelic, tri-allelic mutations or compound mutations with other genes. Recurrent DUOX2 mutations include K530X, R683L, R1110Q, and L1343F. Truncating, splicing, and proven deleterious DUOX2 missense mutations were detected in 50% of the patients. Mutations in TG gene were identified in four patients, and mutations in TPO, THSR, SLC26A4 genes were identified, one in each patient, respectively. The high prevalence of DUOX2 mutations in this cohort of children with CH appears striking and surprising. The clinical implications were discussed.

Triagem de hipotireoidismo em crianças - Visão dos médicos da atenção primária à saúde de um município de médio porte

Objetivo: Avaliar quais parâmetros os médicos da atenção primária à saúde do município de São Carlos, SP, Brasil, adotam para realizar triagem de função tireoidiana em crianças e adolescentes, quais exames complementares são solicitados e qual a conduta diante de resultados laboratoriais alterados. Métodos: Estudo transversal descritivo, no qual participaram 26 profissionais, correspondendo a 96,3% de todos os médicos da atenção primária da cidade que atuam no cuidado de crianças e adolescentes. Os participantes responderam por escrito quais as três situações mais frequentes na prática clínica em que indicavam triagem de hipotireoidismo na população pediátrica, quais os exames laboratoriais solicitados nesta avaliação e a qual conduta frente a exames com resultados alterados. Resultados: As situações clínicas mais frequentes apontadas pelos participantes como indicações de avaliação tireoidiana foram: obesidade, com 23 respostas (88,5%); baixa estatura, com 16 (61,5%); e síndrome de Down, com 8 (30,8%). Nove médicos (34,6%) responderam realizar o rastreio pela dosagem de TSH e T4l e outros 9 (34,6%), pela dosagem de TSH isolado. A conduta mais frequente diante de um resultado alterado foi o encaminhamento ao endocrinologista pediátrico, com 14 respostas (53,8%). Conclusão: O cenário encontrado neste estudo mostra que exames de função tireoidiana são solicitados rotineiramente por médicos da atenção primária no acompanhamento de crianças obesas. Como a obesidade infantil tem uma alta prevalência, isso pode determinar aumento importante dos custos do serviço de saúde e sobrecarga nos serviços de atenção especializada.

Iodine status and thyroid function among Spanish schoolchildren aged 6-7 years: the Tirokid study

I deficiency is still a worldwide public health problem, with children being especially vulnerable. No nationwide study had been conducted to assess the I status of Spanish children, and thus an observational, multicentre and cross-sectional study was conducted in Spain to assess the I status and thyroid function in schoolchildren aged 6-7 years. The median urinary I (UI) and thyroid-stimulating hormone (TSH) levels in whole blood were used to assess the I status and thyroid function, respectively. A FFQ was used to determine the consumption of I-rich foods. A total of 1981 schoolchildren (52 % male) were included. The median UI was 173 μg/l, and 17·9 % of children showed UI<100 μg/l. The median UI was higher in males (180·8 v. 153·6 μg/l; P<0·001). Iodised salt (IS) intake at home was 69·8 %. IS consumption and intakes of ≥2 glasses of milk or 1 cup of yogurt/d were associated with significantly higher median UI. Median TSH was 0·90 mU/l and was higher in females (0·98 v. 0·83; P<0·001). In total, 0·5 % of children had known hypothyroidism (derived from the questionnaire) and 7·6 % had TSH levels above reference values. Median TSH was higher in schoolchildren with family history of hypothyroidism. I intake was adequate in Spanish schoolchildren. However, no correlation was found between TSH and median UI in any geographical area. The prevalence of TSH above reference values was high and its association with thyroid autoimmunity should be determined. Further assessment of thyroid autoimmunity in Spanish schoolchildren is desirable.

Functional characterization of the novel sequence variant p.S304R in the hinge region of TSHR in a congenital hypothyroidism patients and analogy with other formerly known mutations of this gene portion

CONTEXT

Thyroid dysgenesis may be associated with loss-of-function mutations in the thyrotropin receptor (TSHR) gene.

OBJECTIVES

The aim of this study was to characterize a novel TSHR gene variant found in one patient harboring congenital hypothyroidism (CH) from a cohort of patients with various types of thyroid defects.

MATERIALS AND METHODS

This cross-sectional cohort study involved 118 patients with CH and their family members, including 45 with familial and 73 with sporadic diseases. The thyroid gland was normal in 23 patients, 25 patients had hypoplasia, 25 hemithyroid agenesis, 21 had athyreosis, and 21 had ectopy. Genomic DNA was extracted, and 10 exons of the TSHR gene were amplified and sequenced. Mutations in other candidate genes were investigated. Ortholog alignment was performed, and TSHR functional assays were evaluated.

RESULTS

We identified one previously unknown missense variation in the hinge region (HinR) of the TSHR gene (p.S304R) in one patient with thyroid hypoplasia. This variant is conserved in our ortholog alignment. However, the p.S304R TSHR variant presented a normal glycosylation pattern and signal transduction activity in functional analysis.

CONCLUSION

We report the ocurrence of a novel nonsynonymous substitution in the HinR of the large N-terminal extracellular domain of the TSHR gene in a patient with thyroid hypoplasia. In contrast with four others in whom TSHR mutations of the hinge portion were previously identified, the p.S304R TSHR variation neither affected TSH binding nor cAMP pathway activation. This TSHR gene variant was documented in a CH patient, but the current data do not support its role in the clinical phenotype.

The debate on the link between subclinical hypothyroidism and childhood migraine: is initial endocrinological evaluation necessary for children with migraine?

Subclinical hypothyroidism (SH) is characterized by mildly elevated thyroid stimulating hormone (TSH) levels with normal serum-free thyroxine (fT4). While the prevalence of SH is 2 % in pediatric population, it has been reported much higher in children with migraine headache. In this study, the presence of subclinical hypothyroidism and associated endocrinological abnormalities in children with migraine naïve to treatment was investigated. Children with migraine who were diagnosed in Pediatric Neurology Clinic based on the second edition of the International Classification of Headache Disorders and who did not receive any medication were recruited in this cross-sectional study. All patients were examined by the same pediatric endocrinologist and anthropometric measurements, systemic blood pressure, pubertal stages were recorded. Fasting serum levels of thyroid function tests, lipids, glucose and insulin were obtained. Ninety-eight children (55 female) with a mean age of 11.45 ± 3.1 years were evaluated. Of those, 39 were prepubertal and 59 were pubertal. Subclinical hypothyroidism (TSH ≥ 5.0 mIU/L with normal fT4) was detected in five patients (5.1 %); none had positive thyroid antibodies. Other conditions were obesity (n = 6), hirsutism (n = 4), short stature (n = 3), polycystic ovaries (PCO, n = 3), precocious puberty (n = 2) and gynecomastia (n = 1). Of five patients with SH, only one had obesity. Our results revealed that the prevalence of SH in children with migraine is not as high as previously reported. Since no significant endocrinologic disturbance was found in those children, we suggest that the initial endocrinological evaluation or screening for SH is unnecessary.

Thyroid hormonal status among children with obesity

BACKGROUND

It is presumed that free T4 and thyroid-stimulating hormone (TSH) levels are related to obesity, but the findings are inconsistent. In this study we evaluated T4 and TSH concentrations between normal children and those with obesity and possible correlations between body mass index (BMI) and these markers.

METHODS

In this prospective study, 190 children who were overweight and obese and 133 children without obesity of the same age and sex were evaluated. Thyroid function tests (TSH, total T4, free T4 and free T3) were measured in all subjects in both groups. Thyroid antibodies (thyroid peroxidase and thyroglobulin) were determined among those with elevated TSH levels.

RESULTS

Levels of TSH and total T4 were significantly higher in children with obesity compared with the control group. Subclinical hypothyroidism was significantly higher in children with obesity (14.7%) compared with normal subjects (6.8%, p = 0.02). Among children with obesity and increased TSH levels, 10.7% had positive thyroid peroxidase and thyroglobulin antibodies. There was significantly positive correlation between BMI z score and TSH level (r = 0.198, p < 0.001) and T4 level (r = 0.18, p = 0.001).

CONCLUSION

TSH and total T4 levels are increased in children who are overweight or obese and are a common finding in these children, but the incidence of thyroid antibodies is low in these patients and so could not be accounted for by thyroid autoimmunity. Due to these findings it is possible that increased TSH and total T4 levels are a consequence of obesity and could be reduced by decreasing BMI.

Thyrotropin and obesity: increased adipose triglyceride content through glycerol-3-phosphate acyltransferase 3

Epidemiological evidence indicates that thyrotropin (TSH) is positively correlated with the severity of obesity. However, the mechanism remains unclear. Here, we show that TSH promoted triglyceride (TG) synthesis in differentiated adipocytes in a thyroid hormone-independent manner. Mice with subclinical hypothyroidism, which is characterized by elevated serum TSH but not thyroid hormone levels, demonstrated a 35% increase in the total white adipose mass compared with their wild-type littermates. Interestingly, Tshr KO mice, which had normal thyroid hormone levels after thyroid hormone supplementation, resisted high-fat diet-induced obesity. TSH could directly induce the activity of glycerol-3-phosphate-acyltransferase 3 (GPAT3), the rate-limiting enzyme in TG synthesis, in differentiated 3T3-L1 adipocytes. However, following either the knockdown of Tshr and PPARγ or the constitutive activation of AMPK, the changes to TSH-triggered GPAT3 activity and adipogenesis disappeared. The over-expression of PPARγ or the expression of an AMPK dominant negative mutant reversed the TSH-induced changes. Thus, TSH acted as a previously unrecognized master regulator of adipogenesis, indicating that modification of the AMPK/PPARγ/GPAT3 axis via the TSH receptor might serve as a potential therapeutic target for obesity.

Subclinical hypothyroidism in children and adolescents: is it clinically relevant?

Although subclinical hypothyroidism (SH) is a common clinical problem, its diagnosis tends to be incidental. According to the definition, it should be asymptomatic, only detectable by screening. The presence or coincidence of any symptoms leads to L-thyroxine treatment. The clinical presentation, especially in younger patients with subclinical hypothyroidism, is still under dispute. Accordingly, the aim of this paper was to review the literature from the past seven years. The literature search identified 1,594 potentially relevant articles, of which 24 met the inclusion criteria. Few studies focus on the symptomatology of subclinical hypothyroidism, and most of them analyzed a small number of subjects. A significant correlation was found by some authors between subclinical hypothyroidism and a higher risk of hypertension, dyslipidemia, and migraine. No evidence of the impact of subclinical hypothyroidism on weight, growth velocity, and puberty was revealed. As the quality of most studies is poor and no definite conclusions can be drawn, randomized, large-scale studies in children and adolescents are warranted to determine the best care for patients with SH.

Lack of association between peripheral activity of thyroid hormones and elevated TSH levels in childhood obesity

OBJECTIVE

An elevated thyroid stimulating hormone (TSH) level is a frequent finding in obese children, but its association with peripheral hormone metabolism is not fully understood. We hypothesized that in obesity, the changes in thyroid hormone metabolism in peripheral tissues might lead to dysregulation in the thyroid axis. The purpose of this study was to investigate the association of TSH with thyroid hormones in a group of obese children as compared to normal-weight controls.

METHODS

Serum TSH, free thyroxine (fT4) and free triiodothyronine (fT3) levels were measured in 101 obese children and in 40 controls. Serum reverse T3 (rT3) levels were also measured in a subgroup of 51 obese children and in 15 controls.

RESULTS

Serum TSH level was significantly higher in obese children compared to controls (2.78 vs. 1.99 mIU/L, p<0.001), while no difference was found in fT4, fT3, rT3 levels and in fT3/rT3 ratio. In the obese group, fT3 level positively correlated with fT4 (r=0.217, p=0.033) and inversely with rT3 (r=-0.288, p=0.045). However, thyroid hormone levels and TSH levels were not correlated.

CONCLUSION

In obese children, normal fT4, fT3 and rT3 levels suggest an undisturbed peripheral hormone metabolism. These levels show no correlation with elevated TSH levels.

2014 European thyroid association guidelines for the management of subclinical hypothyroidism in pregnancy and in children

This guideline has been produced as the official statement of the European Thyroid Association guideline committee. Subclinical hypothyroidism (SCH) in pregnancy is defined as a thyroid-stimulating hormone (TSH) level above the pregnancy-related reference range with a normal serum thyroxine concentration. Isolated hypothyroxinaemia (defined as a thyroxine level below the 2.5th centile of the pregnancy-related reference range with a normal TSH level) is also recognized in pregnancy. In the majority of SCH the cause is autoimmune thyroiditis but may also be due to iodine deficiency. The cause of isolated hypothyroxinaemia is usually not apparent, but iodine deficiency may be a factor. SCH and isolated hypothyroxinaemia are both associated with adverse obstetric outcomes. Levothyroxine therapy may ameliorate some of these with SCH but not in isolated hypothyroxinaemia. SCH and isolated hypothyroxinaemia are both associated with neuro-intellectual impairment of the child, but there is no evidence that maternal levothyroxine therapy improves this outcome. Targeted antenatal screening for thyroid function will miss a substantial percentage of women with thyroid dysfunction. In children SCH (serum TSH concentration >5.5-10 mU/l) normalizes in >70% and persists in the majority of the remaining patients over the subsequent 5 years, but rarely worsens. There is a lack of studies examining the impact of SCH on the neuropsychological development of children under the age of 3 years. In older children, the evidence for an association between SCH and impaired neuropsychological development is inconsistent. Good quality studies examining the effect of treatment of SCH in children are lacking.

Genetics of normal and abnormal thyroid development in humans

The most frequent cause of congenital hypothyroidism is thyroid dysgenesis. Thyroid dysgenesis summarizes a spectrum of developmental abnormalities of the embryonic thyroid ranging from complete absence of the thyroid gland (athyreosis), to a normally located but too small thyroid (hypoplasia), or an abnormally located thyroid gland (ectopy). Although considered a sporadic disease, distinct genetic forms of isolated or syndromic thyroid dysgenesis have been described in recent years. However, genetics of thyroid dysgenesis (TD) are mostly not following simple Mendelian patterns, and beside monogenic, multigenic and epigenetic mechanisms need to be considered. The review will highlight the molecular mechanisms of thyroid organogenesis, clinical and genetic features of the different monogenetic forms of thyroid dysgenesis, the aspects relevant for diagnosis and counseling of affected families and current research strategies to get more insight into the non-Medelian mechanisms of normal and abnormal thyroid development.

Correlation and presentation of thyroid functional status with thyroid autoantibodies in long-term follow-up of autoimmune thyroiditis: A study of 116 cases

BACKGROUND/PURPOSE

The most common diagnostic finding of autoimmune thyroid disease (AITD) is the presence of antithyroid antibodies. While autoimmune thyroiditis (AT) is a common AITD, aspiration cytology is one of the important diagnostic tools of AT.

METHODS

We evaluated 116 AT patients with ultrasound-guided aspiration cytology and then analyzed the correlation between thyroid hormone status and thyroid autoantibodies. This was a retrospective analysis with prospective collection of data with a mean follow-up period of 68.8 ± 37.8 months. The patients were classified as either euthyroid, hypothyroid, or hyperthyroid (HT). Of the 116 patients, 22 were hypothyroid, 37 were euthyroid, and 57 were HT.

RESULTS

During the follow-up period, 95.5% of the hypothyroid group remained hypothyroid and only one patient improved to euthyroid. In the euthyroid group, 16.2% progressed to hypothyroid and 83.8% remained euthyroid. In the HT group, 8.7% progressed to hypothyroid, 70.2% progressed to euthyroid, and 21.1% remained HT. Most patients with a high titer of thyroglobulin antibody (TgAb) will progress to hypothyroid, and patients with a high titer of thyroid stimulating hormone (TSH) receptor antibody (TRAb) will remain HT. Strong correlations between thyroid functional status and positive number of thyroid autoantibodies were seen in this study. Patients with all the three antibodies positive had a high prevalence of hyperthyroidism.

CONCLUSION

In our study, most patients were HT; this may be because of the early diagnosis and treatment of AT in our clinic. Although antithyroperoxidase antibody (TPOAb) is a hallmark antibody of HT, it cannot predict the initial presentation and clinical outcome.

The W520X mutation in the TSHR gene brings on subclinical hypothyroidism through an haploinsufficiency mechanism

BACKGROUND

TSHR is a G-protein-coupled seven transmembrane domain receptor that activates the two major signal transduction pathways: the Gαs/adenylate cyclase and the Gαq/11/phospholipase C pathways. Inactivating mutations in the TSHR gene have been demonstrated to be responsible for subclinical hypothyroidism, a disorder characterized by elevated serum TSH concentrations despite normal thyroid hormones levels.

AIM

We identified in a child a nonsense mutation (W520X) in the third transmembrane domain of the TSHR that causes the lack of the C-terminus portion of the receptor. The functional significance of this variation was assessed in vitro.

MATERIAL/SUBJECT AND METHODS

The W520X mutation was introduced into the pSVL vector containing the wild-type sequence of TSHR gene. Wild-type and mutated vectors were expressed in Chinese Hamster Ovary (CHO) cells, and cAMP, inositol phosphate (IP), immunofluorescence and FACS analyses were performed.

RESULTS

Transfection with pSVL-TSHR vector induced basal cAMP and IP production in the absence of TSH stimulation, indicating a constitutive activity for the TSHR. An impairment of receptor function was demonstrated by the observation that cells expressing the mutant TSHR exhibited a lower second messenger production with respect to the wild-type, despite a normal expression of the receptor at the cell surface.

CONCLUSIONS

The mechanism through which the W520X mutation exerts its effect is more likely haploinsufficiency rather than a dominant-negative effect. This could explain the phenotype of our patient, who has a hormonal pattern in the range of a mild subclinical hypothyroidism, without an overt disease phenotype.

Subclinical hypothyroidism and myocardial function in obese children

BACKGROUND AND AIMS

Pediatric obesity is an important health problem representing a major public health concern worldwide in the last decades. An isolated elevation of Thyroid Stimulating Hormone (TSH) with normal levels of thyroid hormones is frequently found in obese children. It has been named Isolated Hyperthyreotropinemia or Subclinical Hypothyroidism (SCH) and may be considered a consequence of obesity. Evidence exists that SCH is related to impairment of both systolic and diastolic myocardial function in the adult population. The aim of our study is to establish if obesity-related SCH influences myocardial function in children.

METHODS AND RESULTS

We examined 34 obese children and adolescents with SCH and 60 obese children with normal TSH levels who underwent Doppler echocardiographic to evaluate myocardial function. Global systolic function as assessed by Ejection Fraction (EF) was comparable between groups, however Right Ventricle pressure global systolic function and pressure were significantly reduced in SCH group. Mitral annulus peak systolic (MAPSE) excursion lateral and MAPSE septum resulted significantly reduced in SCH group. Tissue Doppler imaging peak systolic motion (TDI-S) was reduced in SCH group. Diastolic function also showed significant modifications in SCH group.

CONCLUSION

These results suggest possible involvement of cardiac function in obese children with SCH resulting in both abnormal diastolic function and reduced longitudinal systolic function. This new insight into cardiovascular consequences of obesity-related SCH in children could influence clinical approach to such patients by pediatric endocrinologists.

The molecular causes of thyroid dysgenesis: a systematic review

BACKGROUND

Congenital hypothyroidism (CH) is a frequent disease occurring with an incidence of about 1/2500 newborns/year. In 80-85% of the cases CH is caused by alterations in thyroid morphogenesis, generally indicated by the term "thyroid dysgenesis" (TD). TD is generally a sporadic disease, but in about 5% of the cases a genetic origin has been demonstrated. In these cases, mutations in genes playing a role during thyroid morphogenesis (NKX2-1, PAX8, FOXE1, NKX2-5, TSHR) have been reported.

AIM

This work reviews the main steps of thyroid morphogenesis and all the genetic alterations associated with TD and published in the literature.

Subclinical non-autoimmune hypothyroidism in children with steroid resistant nephrotic syndrome

BACKGROUND

Thyroid status has not been studied well in children with steroid resistant nephrotic syndrome (SRNS).

METHODS

In this cross sectional study we recruited 20 children aged 1-16 years with SRNS and similar number of controls. Serum levels of FT3, FT4 and TSH were measured in all the subjects. Overt hypothyroidism was defined as low FT4 (normal values: 0.7-2.0 ng/mL) and elevated serum TSH above reference values (0.45-4.5 mIU/L). Subclinical hypothyroidism (SH) was defined as an elevation in serum TSH with a normal serum FT4 concentration. The primary outcome measure was serum levels of FT3, FT4 and TSH in children with SRNS.

RESULTS

Thirty per cent of the children (n = 6) with SRNS had non-autoimmune subclinical hypothyroidism (2 children each with grade I, II and III). Children with SRNS had a median TSH value [3.9 mIU/L (0.5-13)] within normal range, but levels were high as compared to controls. Out of 6 children with SH, 3 were in partial remission, 3 were in complete remission. The TSH levels normalized on thyroxine supplementation in grades II and III subclinical hypothyroidism.

CONCLUSION

Subclinical non-autoimmune hypothyroidism is present in a significant proportion of children with SRNS despite partial or complete remission. Thyroid profile should be evaluated routinely in this subset of patients.

Early adiposity rebound and obesity in children with congenital hypothyroidism

BACKGROUND

Earlier adiposity rebound (AR) is correlated with obesity. Our goal is to examine rates of obesity and AR in congenital hypothyroidism (CHT) and analyze the risk factors of obesity.

METHODS

We retrospectively reviewed the cases with abnormal newborn screens of thyroid-stimulating hormone (TSH) from 1990 to 2005 and enrolled permanent CHT patients who continued to receive treatment after the 3(rd) year of life. We determined subgroups of obesity/being overweight and normal body mass index (BMI) by the latest BMI at 6-7 years of age. BMI at each age and the age of AR were compared with the general population in Taiwan. The statistical correlation of obesity with the age and BMI at both AR and first peak, and thyroid function was calculated.

RESULTS

A total of 90 cases of CHT were enrolled. The prevalence of obesity/being overweight was 32.2%. The age of AR was 4.94 ± 1.81 and 4.58 ± 1.86 years old in boys and girls, respectively. The age of AR in the girls with CHT was earlier than in girls in general, but no statistical significance was found in boys with CHT compared to the general population. Obesity was correlated with earlier age of AR, higher BMI at first peak and AR, and lower T4 after treatment, but not with the age of first peak of BMI, T4/TSH at diagnosis and AR, and TSH after treatment.

CONCLUSION

Children with CHT have a higher risk of obesity due to earlier age of AR. We recommend that supervision and intervention on weight control should be provided to prevent the occurrence of obesity later.

Maternal thyroid dysfunction during pregnancy and thyroid function of her child in adolescence

CONTEXT

Normal maternal thyroid function is important for fetal development. No knowledge exists on how maternal thyroid function and thyroid antibodies during early pregnancy affect thyroid function of the offspring.

OBJECTIVE

The aim of this study was to investigate the relationship between maternal and adolescent thyroid function parameters.

DESIGN, SETTING, AND PARTICIPANTS

A total of 3673 mother-child pairs from the prospective, population-based Northern Finland Birth Cohort 1986 participated in the study. Maternal serum samples were drawn in early pregnancy (<20th gestational week), and children's samples were drawn at the age of 16 years and analyzed for TSH, free T4 (fT4), and thyroid peroxidase antibodies (TPO-Abs).

MAIN OUTCOME MEASURES

TSH, fT4, and TPO-Ab concentrations were measured at the age of 16 years. Children of mothers with thyroid dysfunction (hypothyroidism, hyperthyroidism, or hypothyroxinemia) or TPO-Ab positivity were compared to those of euthyroid or TPO-Ab-negative mothers. The distributions are expressed as medians with 5th to 95th percentiles.

RESULTS

Boys of hypothyroid mothers had higher TSH concentrations than those of euthyroid mothers: 2.0 (0.9-4.0) vs 1.7 (0.8-3.3) mU/L; P = .001. Children of hyperthyroid mothers had lower TSH concentrations than those of euthyroid mothers: 1.3 (0.6-4.2) vs 1.7 (0.8-3.3) mU/L, P = .013, for boys; and 1.3 (0.5-3.5) vs 1.6 (0.7-3.4) mU/L, P = .034, for girls. There were no differences in TSH or fT4 concentrations between children of hypothyroxinemic and euthyroid mothers. TPO-Ab-positive mothers more often had TPO-Ab-positive children (prevalence, 9.0 vs 3.7% among boys, and 22.7 vs 7.5% among girls).

CONCLUSIONS

Maternal thyroid dysfunction and TPO-Ab positivity during pregnancy seem to modify thyroid function parameters of offspring even in adolescence. Whether this increases the thyroid disease risk of the children is still unknown.

TSH and free triiodothyronine concentrations are associated with weight loss in a lifestyle intervention and weight regain afterwards in obese children

OBJECTIVE

The impact of thyroid hormones on weight loss in lifestyle interventions and on weight regain afterwards is unknown. Therefore, we studied the relationships between TSH, free triiodothyronine (fT₃), free thyroxine (fT₄), and weight status, as well as their changes during and after a lifestyle intervention in obese children.

MATERIALS AND METHODS

We evaluated the weight status as BMI-SDS in 477 obese children (mean age 10.6±2.7 years, 46% male, mean BMI 28.1±4.5  kg/m²) participating in a 1-year lifestyle intervention in a 2-year longitudinal study. Changes in BMI-SDS at 1 and 2 years were correlated with TSH, fT₃, and fT₄ concentrations at baseline and their changes during the intervention.

RESULTS

A decrease in BMI-SDS during the intervention period (-0.32±0.38; P<0.001) was significantly positively associated with baseline TSH and fT₃ in multiple linear regression analyses adjusted for age, sex, pubertal stage, and baseline BMI-SDS. An increase in BMI-SDS after the end of the intervention (+0.05±0.36; P=0.011) was significantly related to the decreases in TSH and fT₃ during the intervention in multiple linear regression analyses adjusted for change in BMI-SDS during the intervention. In contrast to children with weight maintenance, children with weight regain after the end of the intervention demonstrated a decrease in their TSH levels (-0.1±1.6 vs +0.2±1.6  mU/l; P=0.03) and fT₃ (-0.2±1.1 vs +0.3±1.6  pg/ml; P<0.001) during the intervention.

CONCLUSIONS

The decreases in TSH and fT₃ concentrations during the lifestyle intervention were associated with weight regain after the intervention. Future studies should confirm that the decreases in TSH and fT₃ levels associated with weight loss are related to the change in metabolism such as resting energy expenditure.

Current loss-of-function mutations in the thyrotropin receptor gene: when to investigate, clinical effects, and treatment

Thyroid-stimulating hormone receptor (TSHR) loss-of-function (LOF) mutations lead to a wide spectrum of phenotypes, ranging from severe congenital hypothyroidism (CH) to mild euthyroid hyperthyrotropinemia. The degree of TSH resistance depends on the severity of the impairment of the receptor function caused by the mutation and on the number of mutated alleles In this review data about genotype-phenotype correlation and criteria for clinical work-up will be presented and discussed. Complete TSH resistance due to biallelic LOF TSHR mutations must be suspected in all patients with severe not syndromic CH and severe thyroid hypoplasia diagnosed at birth by neonatal screening. Partial forms of TSH resistance show a more heterogeneous hormonal and clinical pattern . In these cases TSH serum levels are above the upper limit of normal range for the age but with a very variable pattern, free thyroxine (T4) concentrations are within the normal range and thyroid size can be normal or hypoplastic at ultrasound scan. An early substitutive treatment with L-T4 must be mandatory in all patients with severe CH due to complete uncompensated TSH resistance diagnosed at birth by neonatal screening. The usefulness of substitutive treatment appears much more controversial inpatients with subclinical hypothyroidism due to partial TSH resistance in whom the increased TSH concentration should be able to compensate the mild functional impairment of the mutant receptor. Together with standard criteria we recommend also an accurate clinical work-up to select patients who are candidates for a LOF TSHR mutation.

Non-autoimmune subclinical hypothyroidism due to a mutation in TSH receptor: report on two brothers

Subclinical hypothyroidism (SH) is a condition characterized by a mild persistent thyroid failure. The main cause is represented by autoimmune thyroiditis, but mutations in genes encoding proteins involved in TSH pathway are thought to be responsible for SH, particularly in cases arising in familial settings. Patients with the syndrome of TSH unresponsiveness may have compensated or overt hypothyroidism with a wide spectrum of clinical and morphological alterations depending on the degree of impairment of TSH-receptor (TSH-R) function. We describe the case of two brothers with non autoimmune SH carrying the same heterozygous mutation in the extracellular domain of TSH-R and presenting with different clinical, biochemical and morphological features. The first one had only a slight persistent elevation of TSH, a normal thyroid ultrasound and did never require l- thyroxine (L-T4) replacement treatment. The second one had a neonatal persistent moderate TSH levels increase associated with a thyroid gland hypoplasia and was treated with L-T4 since the first months of life.

These two cases support the recent association of TSH-R mutations inheritance as an autosomal dominant pattern with variable expressivity and suggest that the decision to start replacement therapy in patients with persistent SH due to TSH resistance should be individualized.

Endocrine disorders in childhood and adolescence. Natural history of subclinical hypothyroidism in children and adolescents and potential effects of replacement therapy: a review

OBJECTIVE

Subclinical hypothyroidism (SH) is quite common in children and adolescents. The natural history of this condition and the potential effects of replacement therapy need to be known to properly manage SH. The aim of this review is to analyze: i) the spontaneous evolution of SH, in terms of the rate of reversion to euthyroidism, the persistence of SH, or the progression to over hypothyroidism; and ii) the effects of replacement therapy, with respect to auxological data, thyroid volume, and neuropsychological functions.

METHODS

We systematically searched PubMed, Cochrane, and EMBASE (1990-2012) and identified 39 potentially relevant articles of which only 15 articles were suitable to be included.

RESULTS AND CONCLUSIONS

SH in children is a remitting process with a low risk of evolution toward overt hypothyroidism. Most of the subjects reverted to euthyroidism or remained SH, with a rate of evolution toward overt hypothyroidism ranging between 0 and 28.8%, being 50% in only one study (nine articles). The initial presence of goiter and elevated thyroglobulin antibodies, the presence of celiac disease, and a progressive increase in thyroperoxidase antibodies and TSH value predict a progression toward overt hypothyroidism. Replacement therapy is not justified in children with SH but with TSH 5-10 mIU/l, no goiter, and negative antithyroid antibodies. An increased growth velocity was observed in children treated with levothyroxine (l-T(4); two articles). l-T(4) reduced thyroid volume in 25-100% of children with SH and autoimmune thyroiditis (two studies). No effects on neuropsychological functions (one study) and posttreatment evolution of SH (one study) were reported.

Subclinical hypothyroidism in children

The prevalence of SH in the pediatric population is < 2%, the caveat being the limited number of studies addressing SCH in the pediatric population. congenital deveolopental anamolies. Mutations in the several proteins are important causes of this condition. Despite the limited data available, SCH in children and adolescents appears to be a benign and remitting disease with a low risk of evolution to OH. It appears that thyroid hormones appear to be functioning well despite elevated TSH. Predictors of progression include, goiter, celiac disease, and positive anti TPO.

Consecutive mutational events in a TSHR allele of Arab families with resistance to thyroid stimulating hormone

BACKGROUND

Our laboratory identified six distinct inactivating TSHR gene mutations in Arab tribes living in Israel. We recently reported three nucleotide substitutions in exon 3 producing p.[L89L;Q90P] and one in exon 9 of the same allele producing p.P264S in Family A. Family B, reported herein, harbors the identical mutation in exon 3 only. We set to determine whether the mutations have common ancestral origin.

METHODS

Coding regions of the TSHR were sequenced and flanking microsatellite markers spanning 5.3 cM were used for haplotyping.

RESULTS

Two siblings of Family B were compound heterozygous for TSHR gene mutations. The paternal allele contained the exon 3 mutation and the maternal allele harbored a mutation in exon 10 (p.L653V). We investigated the possibility of a founder effect with subsequent mutational events for the presence of the same exon 3 mutation in different families. The haplotype of the allele harboring the exon 3 mutation in Family B was identical to that of Family A, also harboring the exon 9 mutation on the same allele, indicating that the latter occurred subsequently. The ancestral wild-type TSHR was present in Family B, suggesting that the mutation in exon 3 was also new in the history of that population.

CONCLUSIONS

It is more likely that two consecutive mutational events occurred on the ancestral wild-type allele instead of a recombination bringing exon 3 and exon 9 mutations together on the same allele. New mutational events contribute to the high prevalence of TSHR mutations in this population in addition to a founder effect and limited gene pool due to inbreeding.

Thyroid function in childhood obesity and metabolic comorbidity

Childhood obesity is a worldwide health problem and its prevalence is increasing steadily and dramatically all over the world. Obese subjects have a much greater likelihood than normal-weight children of acquiring dyslipidemia, elevated blood pressure, and impaired glucose metabolism, which significantly increase their risk of cardiovascular and metabolic diseases. Elevated TSH concentrations in association with normal or slightly elevated free T4 and/or free T3 levels have been consistently found in obese subjects, but the mechanisms underlying these thyroid hormonal changes are still unclear. Whether higher TSH in childhood obesity is adaptive, increasing metabolic rate in an attempt to reduce further weight gain, or indicates subclinical hypothyroidism or resistance and thereby contributes to lipid and/or glucose dysmetabolism, remains controversial. This review highlights current evidence on thyroid involvement in obese children and discusses the current controversy regarding the relationship between thyroid hormonal derangements and obesity-related metabolic changes (hypertension, dyslipidemia, hyperglycemia and insulin resistance, nonalcoholic fatty liver disease) in such population. Moreover, the possible mechanisms linking thyroid dysfunction and pediatric obesity are reviewed. Finally, the potential role of lifestyle intervention as well as of therapy with thyroid hormone in the treatment of thyroid abnormalities in childhood obesity is discussed.

Thyroid function in the nutritionally obese child and adolescent

PURPOSE OF REVIEW

In recent years, there has been an increasing focus on thyroid function in obese children. There is controversy concerning whether the changes in the levels of thyroid hormones and thyroid-stimulating hormone (thyrotropin - TSH) in obesity are causes or consequences of weight status and whether these subtle differences merit treatment with thyroxine. This review aimed to study the prevalence of disturbed thyroid hormone and TSH values in childhood obesity and the underlying pathophysiologic mechanisms linking obesity to thyroid function.

RECENT FINDINGS

In the past 18 months, four studies demonstrated moderate elevation of TSH concentrations in 10-23% of obese children, which was associated with normal or slightly elevated thyroxine and triiodothyronine values. Two studies reported ultrasonographic hypoechogenicity of the thyroid in obese children with hyperthyrotropinemia, which was not caused by autoimmune thyroiditis; therefore, the authors hypothesized a link to chronic inflammation in obesity. Weight loss led to a normalization of elevated TSH levels in two studies. The adipokine leptin is the most promising link between obesity and hyperthyrotropinemia since leptin stimulates the hypothalamic-pituitary-thyroid.

SUMMARY

The elevated TSH levels in obesity seem a consequence rather than a cause of obesity. Therefore, treatment of hyperthyrotropinemia with thyroxine seems unnecessary in obese children.