A newly identified insertion mutation in the thyroid hormone receptor-beta gene in a Korean family with generalized thyroid hormone resistance

An overview of thyroid function tests in subjects with resistance to thyroid hormone and related disorders

Confirmation of sustained syndrome of inappropriate secretion of thyrotropin (SITSH) is a milestone in diagnosis of β type of resistance to thyroid hormone (RTHβ). The differential diagnoses of RTHβ include TSH-producing pituitary adenoma (TSHoma) and familial dysalbuminemic hyperthyroxinemia (FDH), which also present SITSH. Recently, patients with RTHα caused by a mutation in thyroid hormone receptor α were reported and they did not present SITSH but a decline in the serum T4/T3 ratio. This review was aimed to overview thyroid function tests in RTH and related disorders. First, the characteristics of the thyroid function in RTHβ, TSHoma, and FDH obtained from a Japanese database are summarized. Second, the degrees of SITSH in patients with truncations and frameshifts were compared with those in patients with single amino acid deletions and single amino acid substitutions obtained from the literature. Third, the degrees of SITSH in homozygous patients were compared with those in heterozygous patients with cognate mutations. Finally, the FT3/FT4 ratios in RTHα are summarized. In principle, the TSH values in FDH were within the normal range and apparent FT4 values in FDH were much higher than in RTHβ and TSHoma. The FT3/FT4 values in RTHβ were significantly lower than in TSHoma. The degrees of SITSH in patients with truncations and frameshifts were more severe than those in patients with single amino acid deletions and single amino acid substitutions, and those in homozygous patients were more severe than those in heterozygous patients with cognate mutations. The FT3/FT4 ratios in RTHα were higher than 1.0.

Hypercholesterolemia in Two Siblings with Resistance to Thyroid Hormones Due to Disease-Causing Variant in Thyroid Hormone Receptor (THRB) Gene

Resistance to thyroid hormone beta (RTHβ) is a syndrome characterized by a reduced response of target tissues to thyroid hormones. In 85% of cases, a pathogenic mutation in the thyroid hormone receptor beta (THRB) gene is found. The clinical picture of RTHβ is very diverse; the most common findings are goiter and tachycardia, but the patients might be clinically euthyroid. The laboratory findings are almost pathognomonic with elevated free thyroxin (fT4) levels and high or normal thyrotropin (TSH) levels; free triiodothyronin (fT3) levels may also be elevated. We present three siblings with THRB mutation (heterozygous disease-variant c.727C>T, p.Arg243Trp); two of them also had hypercholesterolemia, while all three had several other clinical characteristics of RTHβ. This is the first description of the known Slovenian cases with RTHβ due to the pathogenic mutation in the THRB gene. Hypercholesterolemia might be etiologically related with RTHβ, since the severity of hormonal resistance varies among different tissues and hypercholesterolemia in patients with THRB variants might indicate the relatively hypothyroid state of the liver. We suggest that cholesterol levels are measured in all RTHβ patients.

Thyroid hormone resistance syndrome with P453T mutation in thyroid hormone receptor β gene: A pedigree report

RATIONALE

Thyroid hormone resistance syndrome (THRS) is an inherited condition characterized by reduced responsiveness of target tissues to thyroid hormone. Due to their nonspecific symptomatic manifestations, these patients can be misdiagnosed. This study reports a pedigree with THRS caused by a mutation in the thyroid hormone receptor β (THRβ) gene.

PATIENT CONCERN

The proband, a 36-year-old woman at 19+4 weeks of gestation, was referred to our hospital because of abnormal thyroid function results. She was diagnosed with hyperthyroidism in October 2015, and had been treated with methimazole until her pregnancy.

DIAGNOSIS

The proband and 2 of her children were diagnosed with THRS based on genetic analysis. Sequence analysis of the THRβ gene showed a heterozygous mutation C>A located at exon 10. The mutation results in a change in proline for threonine at amino acid position 453, P453T.

INTERVENTIONS

No treatment will fully and specifically correct the defect. All 3 patients were in normal metabolic status, and thus treatment was not required.

OUTCOMES

During a 2-year follow-up period, none of them had any complaints. The 20-year-old son (167 cm in height) and the 18-year-old daughter (150 cm in height) both had low academic performance.

LESSONS

Elevated serum thyroid hormone (TH) levels associated with nonsuppressed thyroid-stimulating hormone (TSH) levels usually leads to the diagnosis of THRS. Genetic analysis provides a short cut to diagnosis and the treatment should be based on the patient's clinical manifestations.

Identification of a novel mutation in the thyroid hormone receptor β gene that causes thyroid hormone resistance syndrome: A case report

Thyroid hormone resistance syndrome is a rare disease in which the level of thyroid hormone is elevated and the level of thyroid stimulating hormone is not suppressed. Mutations in the thyroid hormone receptor β (THRβ) gene are thought to be the primary cause of pathogenesis. In the present study, a Chinese boy of 4 years and 8 months, who had been pre-diagnosed with resistance to thyroid hormone, was assessed for mutations. The clinical features and thyroid function of the proband and his parents were collected and gene mutations were analyzed using DNA sequencing. Gene sequencing showed that the THRβ genes in the parents of the proband were consistent with the standard sequence, however, in the proband there was a mutation in the tenth exon of the THRβ gene (c. 824 T>C). This is a newly identified mutation site and, to the best of our knowledge, there have been no previous reports of this mutation site. Therefore, it is hypothesized that this mutation is the cause of the pathology in the proband.

Thyroid hormone resistance syndrome caused by heterozygous A317T mutation in thyroid hormone receptor β gene: Report of one Chinese pedigree and review of the literature

BACKGROUND

Thyroid hormone resistance syndrome (THRS) is a rare disorder with increased concentrations of free thyroxine (FT4) and triiodothyronine (FT3), but normal or slightly increased thyroid-stimulating hormone (TSH). The mutations in the thyroid hormone receptor β (THRβ) gene are thought to be the main pathogenesis.

OBJECTIVES

The aims of this study were to present 1 pedigree of Chinese THRS, summarize their clinical characteristics, and analyze the gene mutation.

METHODS

The clinical characteristics and thyroid function of the proband and his family members were collected. Gene mutations were analyzed by DNA sequencing.

RESULTS

The proband and his mother exhibited symptoms of hyperthyroidism, such as palpitations, heat intolerance, and perspiration. The mother also had atrial fibrillation. The rest of the kindred did not display clinical manifestations of hyper- or hypothyroidism. DNA sequencing revealed a heterozygous G>A missense mutation at position 949 in Exon 9 of THRβ both in the patient and his mother, which led to the transition from alanine to threonine at position 317 of THRβ protein (A317T), whereas the rest of the kindred did not share this mutation. The proband and his mother were diagnosed with pituitary resistance to thyroid hormone. Oral administration of methimazole was stopped and β-receptor blockers were administrated.

CONCLUSIONS

We present 1 pedigree of THRS with heterozygous A317T mutation in THRβ gene in the proband and his mother, which is the first reported mutation in Chinese and provides a comprehensive review of available literature.

A Rare Mutation in Patients With Resistance to Thyroid Hormone and Review of Therapeutic Strategies

BACKGROUND

Resistance to thyroid hormone (RTH) is a rare syndrome characterized by elevated thyroid hormone (TH) along with nonsuppressed thyroid-stimulating hormone (TSH). The clinical symptoms can vary considerably, and no definite treatment has been established thus far.

METHODS

A family with RTH harboring a TH receptor (THR)-β gene mutation (A234T) is described, the therapeutic strategies for RTH are reviewed, and optimization of the treatment strategies was attempted.

RESULTS

Gene sequencing revealed a point mutation (A234T) in the THR-β gene of the proposita, her elder brother and her mother. During the 20-month follow-up period, it was found that the proposita experienced apparently higher TSH level and normal TH level on taking antithyroid medication. However, on discontinuing the medication, her thyroid function returned to the baseline of elevated FT3, FT4 level along with inappropriately normal TSH. Thus far, there is no guideline regarding the treatment strategies for the RTH. Antithyroid drugs are effective for patients with thyrotoxic symptoms but pose an increased risk of thyrotroph hyperplasia. The efficacy and safety of D-T4 and bromocriptine still remains debatable, TRIAC may be the most promising drug, as it is effective and can reduce both TH and TSH level. However, L-T3 or L-T4 may be necessary for some RTH patients who exhibit massive goiter or hypothyroid symptoms.

CONCLUSIONS

It is demonstrated in this article that the A234T mutation in the THR-β gene can cause the RTH. Treatment of this condition is challenging, and individualized therapy is required because of the variable clinical features.

Resistance to thyroid hormone due to a novel mutation of thyroid hormone receptor beta gene

Resistance to thyroid hormone (RTH) is a rare inherited syndrome characterized by diminished response of the target tissue to thyroid hormone caused, in the majority of cases, by mutation of the thyroid hormone receptor beta (THRβ) gene. Despite elevated serum levels of free thyroid hormones and thyroid stimulating hormone (TSH), the paucity of symptoms and signs of thyroid dysfunction suggest RTH. We report the case of a 9-year-old girl with goiter. Her thyroid function tests showed increased serum levels of free thyroxine, triiodothyronine, and TSH. The genetic analysis of THRβ confirmed a novel mutation in exon 9; this was a heterozygous C-to-T change in the 327th codon, substituting threonine for isoleucine (T327I).

A Case of Resistance to Thyroid Hormone with Chronic Thyroiditis: Discovery of a Novel Mutation (I54V)

Resistance to thyroid hormone (RTH) is a rare disorder characterized by variable tissue hyporesponsiveness to thyroid hormone, usually caused by mutations in the thyroid hormone receptor beta (TRβ). It has been reported that the serum of patients with RTH is free of auto-antibodies against thyroglobulin (Tg) and thyroid peroxidase (TPO), except in rare cases where coincidental autoimmune thyroiditis is also present. We describe a 13-year-old girl with chronic thyroiditis and RTH. This patient had increased plasma free T3, free T4 at the upper limits with unsuppressed TSH. She had peripheral manifestations of thyroid hormone excess, hypertension and growth acceleration. Anti-TPO antibodies were positive. Sequence analysis of the TRβ gene was performed and revealed a novel mutation I54V in exon 4. The same mutation was also found in the mother and two asymptomatic sisters. The clinical presentation of our patient is not habitual in RTH because growth retardation is frequently reported in this syndrome. The association between RTH and thyroiditis complicate the management of the hypothyroidism.

A case of resistance to thyroid hormone with thyroid cancer

Resistance to thyroid hormone (RTH) is an autosomal dominant hereditary disorder that is difficult to diagnose because of its rarity and variable clinical features. The magnitude of RTH is caused by mutations in the thyroid hormone receptor beta (TR beta) gene. We recently treated a 38-yr-old woman with RTH who had incidental papillary thyroid carcinoma. She presented with goiter and displayed elevated thyroid hormone levels with an unsuppressed TSH. She was determined to harbor a missense mutation of M310T in exon 9 of the TR beta gene, and diagnosed with generalized RTH. This mutation has not yet been reported in Korea. RTH is very rare and easily overlooked, but should be considered in patients who present with goiter and elevated thyroid hormone levels with an unsuppressed TSH. The association between thyroid cancer and RTH needs further study.

A novel mutation of thyroid hormone receptor beta (I431V) impairs corepressor release, and induces thyroid hormone resistance syndrome

Resistance to thyroid hormone (RTH) is a rare disorder characterized by variable tissue hyporesponsiveness to thyroid hormone, usually caused by mutations in the thyroid hormone receptor beta (TRbeta). We describe a large Brazilian family harboring a novel mutation affecting TRbeta gene and inducing RTH. A 14-year-old girl was found to have elevated free T4 and free T3 plasma concentrations in coexistence with unsuppressed TSH and a questionable goiter. The diagnosis of RTH was verified by identification of a novel mutation (I431V) in the TRbeta gene. Sixteen asymptomatic relatives of the proposita are also affected by the mutation. Functional studies showed that I431V mutation exerts dominant-negative effect on wild type TRbeta, mainly by impairment of ligand-dependent release of corepressor SMRT. The presence of this mutation reduces potency, but does not affect efficacy of thyroid hormone action, in accordance with the clinical picture of eumetabolism of the affected individuals.