Maternal TSH-receptor antibodies and TSH antibodies in screening for congenital hypothyroidism

A case of macro-TSH consisting of IgA-bound TSH

An asymptomatic, 68-year-old Japanese man visited our hospital for further examination of subclinical hypothyroidism. At the first visit, the serum TSH level was markedly elevated (36.6 μIU/mL), but the serum level of free T4 was within the reference interval. Thyroid dysfunction due to dietary iodine excess was initially suspected. However, even after iodine restriction, his thyroid function tests were the same as at the first visit, which suggested false elevation of the TSH level. The TSH levels were compared among three different measurement systems, which showed a similar tendency of TSH elevation above the reference interval, but the different TSH elevation levels among the measurement methods suggested the existence of some interfering substance. Neither serial dilution of the patient's serum nor polyethylene glycol and protein G precipitation tests showed any significant changes in the recovery rate. IgG-bound macro-TSH was ruled out. The TSH peak on gel filtration chromatography was located at a molecular size greater than IgA, which suggested the presence of IgA-bound TSH. After precipitation with Jacalin, which binds specifically to IgA, the TSH level decreased from 30.7 μIU/mL to 2.01 μIU/mL, within the reference interval. Thus, IgA-bound macro-TSH was identified. Macro-TSH is a rare condition in which an immunoglobulin-bound, high-molecular-weight form of TSH results in a false elevation of the serum TSH level. When there is a discrepancy between the results of thyroid function tests and clinical symptoms, and macro-TSH is suspected, it is necessary to know that not only IgG-bound TSH but also IgA-bound TSH could be the cause.

Update on Neonatal Isolated Hyperthyrotropinemia: A Systematic Review

The purpose of this paper was to systematically summarize the published literature on neonatal isolated hyperthyrotropinemia (HTT), with a focus on prevalence, L-T4 management, re-evaluation of thyroid function during infancy or childhood, etiology including genetic variation, thyroid imaging tests, and developmental outcome. Electronic and manual searches were conducted for relevant publications, and a total of 46 articles were included in this systematic review. The overall prevalence of neonatal HTT was estimated at 0.06%. The occurrence of abnormal imaging tests was found to be higher in the persistent than in the transient condition. A continuous spectrum of thyroid impairment severity can occur because of genetic factors, environmental factors, or a combination of the two. Excessive or insufficient iodine levels were found in 46% and 16% of infants, respectively. Thirty-five different genetic variants have been found in three genes in 37 patients with neonatal HTT of different ethnic backgrounds extracted from studies with variable design. In general, genetic variants reported in the TSHR gene, the most auspicious candidate gene for HTT, may explain the phenotype of the patients. Many practitioners elect to treat infants with HTT to prevent any possible adverse developmental effects. Most patients with thyroid abnormalities and/or carrying monoallelic or biallelic genetic variants have received L-T4 treatment. For all those neonates on treatment with L-T4, it is essential to ensure follow-up until 2 or 3 years of age and to conduct medically supervised trial-off therapy when warranted. TSH levels were found to be elevated following cessation of therapy in 44% of children. Withdrawal of treatment was judged as unsuccessful, and medication was restarted, in 78% of cases. Finally, data extracted from nine studies showed that none of the 94 included patients proved to have a poor developmental outcome (0/94). Among subjects presenting with normal cognitive performance, 82% of cases have received L-T4 therapy. Until now, the precise neurodevelopmental risks posed by mild disease remain uncertain.

Protocol of the PSYCHOTSH study: association between neonatal thyroid stimulating hormone concentration and intellectual, psychomotor and psychosocial development at 4-5 year of age: a retrospective cohort study

Background

Several European countries, including Belgium, still suffer from mild iodine deficiency. Thyroid stimulating hormone (TSH) concentration in whole blood measured at birth has been proposed as an indicator of maternal iodine status during the last trimester of pregnancy. It has been shown that mild iodine deficiency during pregnancy may affect the neurodevelopment of the offspring. In several studies, elevated TSH levels at birth were associated with suboptimal cognitive and psychomotor outcomes among young children. This paper describes the protocol of the PSYCHOTSH study aiming to assess the association between neonatal TSH levels and intellectual, psychomotor and psychosocial development of 4–5 year old children. The results could lead to a reassessment of the recommended cut-off levels of 5 > mU/L used for monitoring iodine status of the population.

Methods

In total, 380 Belgian 4–5 year old preschool children from Brussels and Wallonia with a neonatal blood spot TSH concentration between 0 and 15 mU/L are included in the study. For each sex and TSH-interval (0–1, 1–2, 2–3, 3–4, 4–5, 5–6, 6–7, 7–8, 8–9 and 9–15 mU/L), 19 newborns were randomly selected from all newborns screened by the neonatal screening centre in Brussels in 2008–2009. Infants with congenital hypothyroidism, low birth weight and prematurity were excluded from the study. Neonatal TSH concentration was measured by the Autodelphia method in dried blood spots, collected by heel stick on filter paper 3 to 5 days after birth. Cognitive abilities and psychomotor development are assessed using the Wechsler Preschool and Primary Scale of Intelligence - third edition - and the Charlop-Atwell Scale of Motor coordination. Psychosocial development is measured using the Child Behaviour Check List for age 1½ to 5 years old. In addition, several socioeconomic, parental and child confounding factors are assessed.

Conclusions

This study aims to clarify the effect of mild iodine deficiency during pregnancy on the neurodevelopment of the offspring. Therefore, the results may have important implications for future public health recommendations, policies and practices in food supplementation. In addition, the results may have implications for the use of neonatal TSH screening results for monitoring the population iodine status and may lead to the definition of new TSH cut-offs for determination of the severity of iodine status and for practical use in data reporting by neonatal screening centres.

Mild iodine deficiency in pregnancy in Europe and its consequences for cognitive and psychomotor development of children: a review

Despite the introduction of salt iodization programmes as national measures to control iodine deficiency, several European countries are still suffering from mild iodine deficiency (MID). In iodine sufficient or mildly iodine deficient areas, iodine deficiency during pregnancy frequently appears in case the maternal thyroid gland cannot meet the demand for increasing production of thyroid hormones (TH) and its effect may be damaging for the neurodevelopment of the foetus. MID during pregnancy may lead to hypothyroxinaemia in the mother and/or elevated thyroid-stimulating hormone (TSH) levels in the foetus, and these conditions have been found to be related to mild and subclinical cognitive and psychomotor deficits in neonates, infants and children. The consequences depend upon the timing and severity of the hypothyroxinaemia. However, it needs to be noted that it is difficult to establish a direct link between maternal iodine deficiency and maternal hypothyroxinaemia, as well as between maternal iodine deficiency and elevated neonatal TSH levels at birth. Finally, some studies suggest that iodine supplementation from the first trimester until the end of pregnancy may decrease the risk of cognitive and psychomotor developmental delay in the offspring.

Hypothyroidism associated with anti-human chorionic gonadotropin antibodies secondarily produced by gonadotropin therapy in a case of idiopathic hypothalamic hypogonadism

We report a 22-yr-old male patient with idiopathic hypothalamic hypogonadism who showed secondary resistance to gonadotropin (Gn) therapy over 3 yr after successful treatment with hCG combined with human menopausal Gn. The patient simultaneously developed subclinical hypothyroidism. Endocrine examination revealed low levels of testosterone (0.3 ng/ml), free T4 (0.91 ng/dl), and increased levels of TSH (31.1 microU/ml) in the serum. Serum autoantibodies to thyroid gland were all negative. Interestingly, thyroid function was improved after discontinuation of Gn therapy. In vitro assays by immunoprecipitation using 125I-hCG or 125I-TSH elucidated the presence of anti-hCG antibody in the serum 13 months after commencement of Gn therapy but anti-TSH antibody was not detected in the serum. Furthermore, the anti-hCG antibody specifically bound to hCG but not to other glycoproteins including TSH and FSH based on a competitive displacement assay. Bioassays using porcine thyroid cells revealed that the serum gamma-globulin fraction enables the suppression of cyclic AMP (cAMP) synthesis stimulated by TSH. Our findings suggest that anti-hCG and/or anti-idiotypic hCG antibodies induced by hCG therapy impaired TSH-dependent cAMP production through interfering with binding of TSH to its receptor, and this resulted in subclinical hypothyroidism in this patient.

The differing outcomes of hyperthyrotropinaemia

Hyperthyrotropinaemia, in which normal levels of T4 occur in association with raised TSH, is picked up on neonatal screening. The outcome of children with persistent hyperthyrotropinaemia is uncertain. The study objective was to evaluate the outcome of children with the persistent form of hyperthyrotropinaemia. We carried out a retrospective analysis on children who attended one institution over the last 20 years with this diagnosis. Eight children were diagnosed with hyperthyrotropinaemia lasting more than 3 months in total. Four had a transient form lasting between 3 and 18 months in total. Three continue to have persistently raised TSH at 5, 9 and 17 years, respectively. One patient became biochemically hypothyroid at 1 year of age requiring treatment with replacement thyroxine. All of our group had normal growth and development. We recommend that thyroid function monitoring should continue in all children with hyperthyrotropinaemia until the thyroid function tests have normalised.

Novel thyrotropin (TSH)-TSH antibody complex in a healthy woman and her neonates

A novel high-molecular-weight (MW) form of immunoreactive TSH [35,000 Da on Sephacryl S-200HR gel chromatography (S-200 chromatography)] was documented in a 32-year-old healthy woman who delivered two neonates with transient hyperthyrotropinemia. Her TSH levels ranged from 21.2 to 53.9 mU/L on different days or from 11.0 to 48.1 mU/L by the different immunoradiometric assay methods. The IgG fractions showed specific 125I-labeled hTSH binding and inhibited in vitro cAMP increase induced by hTSH but not that induced by bTSH. On protein G Superose HR affinity chromatography (protein G chromatography) equilibrated with 10 mmol/L sodium/potassium phosphate buffer (PB) followed by elution with 0.1mol/L glycine buffer, 95-99% of her TSH immunoreactivity eluted in the latter (bound) fraction while almost all was in the former (unbound) fraction in the control serum containing authentic hTSH. However, after dialysis of this bound fraction overnight with PB adding 0.5 mol/L NaCl (PB/NaCl), which exhibited greater ionic strength than PB, almost all TSH immunoreactivity changed from the bound fraction into the unbound fraction on the protein G chromatography equilibrated with PB/NaCl. These data indicate that the novel immunoreactive TSH was due to hTSH and hTSH-specific antibody complex, and dissociation of the complex may be incomplete on direct S-200. The immunoreactive TSH showed high MW form (35,000 Da). The dissociation may be almost complete during dialysis with greater ionic strength; the native TSH then appeared to be of formal size.

Thyrotropin receptor antibodies: advances and importance of detection techniques in thyroid diseases

The study of autoimmune thyroid disorders (AITD) has greatly contributed to our knowledge of autoimmunity. Graves' disease and Hashimoto's thyroiditis represent two ends of the range of autoimmune responses seen in AITD. Autoantibodies reactive to cytoplasmic antigens are associated with cell damage, and thyrotropin (TSH)-receptor antibodies (TRAb) influence the function and growth of the gland and play a major role in pathogenesis. The heterogeneous nature of TRAb is well accepted. Besides their long-known thyroid stimulating activity, TRAb can act as blocking antibodies or growth-promoting antibodies and, thus, cause hypothyroidism (primary myxedema) or endemic and sporadic goiters, respectively. Advanced methodologies for detection of these antibodies with the TSH-receptor assay and thyroid cell bioassay allow various activities to be measured. Current data using these assays confirm the presence of heterogeneity of functional activities of TRAb(s) in vivo. The activity of predominating antibody may relate to clinical presentation. This indicates a need for paired determinations of both TSH-binding inhibitory immunoglobulin (TBII) and thyroid-stimulating immunoglobulin (TSI) for accurate clinical correlations. Cloning the TSH-receptor gene has clarified its structure and function. The future identification of its epitopes will further delineate the clinical role of these antibodies and may allow development of new diagnostic and therapeutic approaches.

Circulating thyroid antibodies in congenital hypothyroidism

The role of maternal thyroid antibodies in congenital hypothyroidism is controversial. We have analysed serum thyroid antibodies in patients and their mothers. In a bioassay, antibodies interacting with thyroid cells were analysed by measuring of TSH-stimulated cAMP production in a rat thyroid cell line, FRTL5. Serum antibodies against the TSH receptor, thyroid peroxidase and thyroglobulin were determined by radioreceptor assay and enzyme-linked immunosorbent assays. The bioassay was performed with IgG preparations from 89 mothers of children with congenital hypothyroidism. Analyses for TSH receptor antibodies and thyroid peroxidase/thyroglobulin antibodies were performed on 144 and 118 sera of newborn patients respectively. No evidence of an increased prevalence of thyroid antibodies was found on comparison with controls. One infant had transient neonatal hyperthyrotropinaemia because of TSH receptor blocking antibodies transferred from the mother. Our data indicate that, apart from transplacental transfer of TSH receptor antibodies, maternal immunoglobulins have a limited role in the aetiology of congenital thyroid dysfunction.