Difficulties in diagnosing and managing coexisting primary hypothyroidism and resistance to thyroid hormone

Resistance to thyroid hormone due to a novel mutation in the thyroid beta receptor (THRβ) gene coexisting with autoimmune thyroid disease—A case report

Resistance to thyroid hormone (RTH) is a syndrome characterized by impaired responsiveness of target tissues to thyroid hormones. The relationship between RTHβ and thyroid autoimmunity has been under research. In this study, we demonstrate a case report of a woman with a novel mutation in THRβ gene coexisting with autoimmune thyroid disease (AITD). The 36-year-old woman has been treated since childhood for a thyroid disease. Based on high levels of thyroid hormones (THs) and elevated concentrations of thyroperoxidase and thyroglobulin antibodies (TPOAb and TgAb, respectively), she received unnecessary long-term treatment with methimazole and finally underwent subtotal thyroidectomy. After the surgery, her TSH level remained significantly elevated, despite the treatment with 150 + 15 µg of thyroxine and triiodothyronine. A sequence analysis of the THRβ gene revealed a novel dinucleotide substitution affecting codon 453, resulting in the replacement of the normal proline with an asparagine (c.1357_1358delinsAA, p.(Pro453Asn)). The mutation has not been described in the literature yet; however, THRβ codon 453 represents a mutational hot spot, frequently altered in the TH receptor ß gene. After establishing the diagnosis of RTH, the patient was treated with 300 µg of thyroxine, which showed clinical improvement and normalization of TSH. The coexistence of RTHβ and AITD may additionally impede establishment of a proper diagnosis, leading to unnecessary therapy and delayed correct treatment. The presented case encourages a closer cooperation between clinical endocrinologists and geneticists.

Defective Levothyroxine Response in a Patient with Dyshormonogenic Congenital Hypothyroidism Caused by a Concurrent Pathogenic Variant in Thyroid Hormone Receptor-β

Background: Pituitary resistance to thyroid hormone (PRTH) is often seen in congenital hypothyroidism (CH), presenting as elevated thyrotropin (TSH) values despite (high-)normal thyroid hormone (TH) values achieved by levothyroxine treatment. In this study, we describe a girl with CH who was referred because of difficulties interpreting thyroid function tests. She was thought to have PRTH associated with CH, but genetic studies discovered a pathogenic variant in THRB, causing resistance to TH (RTH-β). Methods: Clinical, genetic, and biochemical data of the proband's family were collected. Results: The 3-year-old girl was diagnosed with CH due to a homozygous pathogenic c.470del p.(Asn157Thrfs*3) SLC5A5 variant in the neonatal period. She needed a notably high levothyroxine dose to normalize TSH, leading to high free thyroxine levels. There were no signs of hyperthyroidism. Sequencing identified a heterozygous pathogenic c.947G>A p.(Arg316His) THRB variant. Conclusions: To our knowledge, this is the first report of concomitant SLC5A5 and THRB variants causing CH and RTH-β.

A case of resistance to thyroid hormone diagnosed after total thyroidectomy for thyroid cancer

This is a case of a woman who was diagnosed with resistance to thyroid hormone after total thyroidectomy for thyroid cancer. Preoperative laboratory examination revealed the syndrome of inappropriate secretion of TSH, however, the patient had no thyrotoxic symptoms and no family history. Based on the results of ultrasonography and fine needle aspiration, she was diagnosed with papillary thyroid carcinoma and underwent total thyroidectomy. After the surgery, she received L-T4 therapy, but her TSH levels remained elevated. MRI was performed on the brain, but no lesions were found in the pituitary gland. Therefore, she was tested for TRβ gene, and a previously defined mutation, P453S, was detected. Ultimately, she was diagnosed as RTH and treated with L-T4. In this case, the dose of L-T4 needed to be increased to suppress her TSH levels to the normal range or less, and to prevent stimulating malignant cells. Currently, her dose of L-T4 has been increased, and her TSH levels are still lower than normal, however, she has no thyrotoxic symptoms, recurrence or metastasis of thyroid cancer. The patient is currently under careful observation regarding her circulatory and physiological status. In addition, the results of treatment still need to be monitored and evaluated.

Management of differentiated thyroid cancer in the presence of resistance to thyroid hormone and TSH-secreting adenomas: a report of four cases and review of the literature

BACKGROUND

An increased or normal serum TSH concentration, despite elevated thyroid hormone levels, is observed in resistance to thyroid hormone (RTH) and TSH-secreting adenomas (TSHomas). When coexistent with a differentiated thyroid cancer (DTC), maintenance of a suppression of TSH is challenging.

OBJECTIVES

The aim of the study was to discuss the pitfalls arising from the failure to suppress TSH secretion in DTC and the strategies for proper treatment of DTC in association with RTH and TSHoma.

METHODS

Four unusual cases of DTC associated with TSHoma (2 cases), RTH (1 case), and an elevated TSH of unknown etiology (1 case) are presented, and the literature is reviewed.

RESULTS

Although a persistent mild TSH elevation may not be a risk factor for the development of DTC, it represents an important problem during the treatment of DTC. Aggressive treatment options should be applied in the proper order to prevent tumor recurrence and persistence in the absence of ideal TSH suppression.

CONCLUSIONS

Although there is no agreed consensus regarding the management of DTC in the presence of persistent hyperthyrotropinemia, complete tumor removal followed by radioablation and attempts to reduce the serum TSH to the lowest tolerable level are recommended. The outcomes in the reported cases have not been unfavorable, despite the persistence of nonsuppressed TSH.

Variable clinical presentation and outcome in pediatric patients with resistance to thyroid hormone (RTH)

Resistance to thyroid hormone (RTH) is characterized by elevated levels of thyroid hormones, normal or slightly increased TSH levels respondent to TRH, resistance to thyroid hormone administration, and variable clinical expression. To describe the diverse clinical and biochemical findings of six children from five unrelated families with molecular diagnosis of RTH (0.5-12.7 years) and their follow-up (3-20 years). All RTH patients and 4 affected parents' harbored mutations in exons 9 or 10 of the thyroid receptor β gene: p.M313T (de novo), pN331D, p.L341P, p.L346F, and p.P453L. At consultation 5/6 had goiter, 4/6 tachycardia, and 3/5 learning disabilities. Median hormone levels were: T(4) 257.4 nmol/l (NR: 77.2-180.2); FreeT(4) 39.9 pmol/(NR:10.3-28.3); T(3) 4.28 nmol/l (NR:1.23-3.39) TSH 2.8 mUI/l (NR: 0.5-5) always responsive to TRH. TSH levels remained detectable after supraphysiologic T(3) administration while SHBG levels showed a paradoxical decrease in 4/6. Thyroid antibodies, initially present in two subjects, became positive in other two during follow-up. All patients grew normally and presented variable symptoms that were treated according to need. Two patients developed psychiatric disorders. Only one of the four affected parents exhibited clinical signs of RTH (tachycardia and depression). Parent's thyroid profile showed similar TSH and T(3) levels but lower T(4) and FT(4) than their children. RTH has a distinctive biochemical profile with highly variable clinical manifestations and outcomes. Its recognition and molecular characterization avoid misleading diagnosis. Treatment has to be instituted according to each subject's own clinical requirements.

Autoimmunity in patients with resistance to thyroid hormone

CONTEXT

Resistance to thyroid hormone (RTH) is an inherited syndrome most often caused by thyroid hormone receptor beta (TRbeta) gene mutations. Given that autoimmune thyroid disease (AITD) is prevalent in the general population, its coexistence with RTH has been presumed coincidental. It was recently proposed that chronic TSH stimulation in RTH may induce an autoimmune response, thereby increasing the chance of their coexistence.

OBJECTIVE

The aim was to examine the prevalence of AITD in a large cohort with RTH compared with their unaffected first-degree relatives.

SUBJECTS AND METHODS

Among 130 families, 330 individuals with RTH confirmed by the presence of TRbeta gene mutations and 92 unaffected first-degree relatives were tested for thyroglobulin and thyroperoxidase antibodies. The presence of AITD was based on at least one of the two antibodies being positive. Data were analyzed according to genotype, gender, age, and familial association. A large homogeneous family was analyzed separately.

RESULTS

Individuals with RTH had an increased likelihood of thyroid autoantibodies (odds ratio = 2.36; P = 0.002). In males, the odds of having AITD were higher in individuals with RTH compared to unaffected first-degree relatives (odds ratio = 2.91; P = 0.042). Although female subjects with RTH had an odds ratio of 1.95 for having thyroid autoantibodies, the difference was not statistically significant (P = 0.097). Antibody prevalence at different ages was not affected by genotype.

CONCLUSIONS

Individuals with RTH due to TRbeta gene mutations have an increased likelihood of AITD compared to unaffected relatives, but the prevalence of thyroid autoantibodies with advancing age is not affected by genotype. These novel findings demonstrate that the association between RTH and AITD is not coincidental.

Genotyping of resistance to thyroid hormone in South American population. Identification of seven novel missense mutations in the human thyroid hormone receptor beta gene

Thyroid Hormone Receptor beta (THRB) defects, typically transmitted as autosomal dominant traits, cause Resistance to Thyroid Hormone (RTH). We analyzed the THRB gene in thirteen South American patients with clinical evidence RTH from eleven unrelated families. Sequence analysis revealed seven novel missense mutations. Four novel mutations were identified in exon 9. The first, a c.991A>G transition which originates a substitution of asparagine by aspartic acid (p.N331D). The second nucleotide alteration consists of a guanine to cytosine transversion at position 1003 (c.1003G>C) and results in substitution of the alanine at codon 335 by proline (p.A335P). The third mutation, a c.1022T>C transition produces a change of leucine by proline (p.L341P). The fourth mutation detected in exon 9 was a c.1036C>T transition which replaces the leucine at codon 346 by phenylalanine (p.L346F). The sequencing of the exon 10 detected three novel missense mutations. The first, a c.1293A>G transition changing isoleucine 431 for methionine (p.I431M). The second, the cytosine at position 1339 was replaced by adenine (c.1339C>A) resulting in the replacement of proline by threonine (p.P447T). The third mutation detected in exon 10 was a c.1358C>T transition resulting in the substitution of proline at codon 453 by leucine (p.P453L). Finally, sequencing analysis of the THRB gene revealed three substitutions previously described (p.A268G, p.P453T and p.F459C). The p.P453T was found in two patients. In conclusion, we report thirteen patients with RTH caused by heterozygous mutations of the THRB gene. Seven of the identified mutations correspond to novel substitutions.

Proposing a causal link between thyroid hormone resistance and primary autoimmune hypothyroidism

Resistance to thyroid hormone (RTH) is a rare, inherited condition. It is characterised by raised circulating fT4 and TSH levels. The literature contains a number of descriptions of the finding of thyroid autoantibodies in patients with RTH. Until now, this has been attributed to the coincidental development of primary autoimmune thyroiditis as a second unrelated pathology. Our hypothesis is that the chronic TSH elevation in RTH stimulates lymphocytes to produce the pro-inflammatory cytokine TNF-alpha. TNF-alpha, in turn mediates thyroid cell destruction by binding to its receptors on thyrocytes, or indirectly by potentiating antibody formation or cytotoxic T lymphocyte production.