Reduced pituitary size in subjects with mutations in the THRB gene and thyroid hormone resistance

Background: Thyroid hormone action is mediated by two forms of thyroid hormone receptors (α,β) with differential tissue distribution. Thyroid hormone receptor β (TRβ) mutations lead to resistance to thyroid hormone action in tissues predominantly expressing the β form of the receptor (pituitary, liver). This study seeks to identify effects of mutant TRβ on pituitary size. Methods: High-resolution 3D T1-weighted magnetic resonance images were acquired in 19 patients with RTHβ in comparison to 19 healthy matched controls. Volumetric measurements of the pituitary gland were performed independently and blinded by four different raters (two neuroradiologists, one neurologist, one neuroscientist). Results: Patients with mutant TRβ (Resistance to Thyroid Hormone β,RΤΗβ) showed elevated fT3/4 levels with normal TSH levels, whereas healthy controls showed normal thyroid hormone levels. Imaging revealed smaller pituitary size in RTHβ patients in comparison to healthy controls (F(1,35)=7.05, p=0.012, partial η2 =0.17). Conclusion: RTHβ subjects have impaired sensitivity to thyroid hormones, along with decreased size of the pituitary gland.

Graves’ disease coexisted with resistance to thyroid hormone: a case report

Background Resistance to thyroid hormone is a rare autosomal dominant disorder characterized by reduced responsiveness to thyroid hormone and can cause syndrome of inappropriate secretion of thyroid stimulating hormone. Although Graves’ disease is a common autoimmune thyroid disorder, the coexistence of these two diseases is extremely rare and makes the diagnosis and treatment complicated, leading to the delayed diagnosis of resistance to thyroid hormone. We describe the case of a Japanese man with resistance to thyroid hormone coexisting with Graves’ disease, in which the correct diagnosis of resistance to thyroid hormone was delayed by masking of the signs of syndrome of inappropriate secretion of thyroid stimulating hormone, with final diagnosis 30 years after the initial treatment for Graves’ disease. Case presentation A 30-year-old Japanese man presented with diffuse goiter and thyrotoxicosis. Anti-thyroid stimulating hormone receptor antibody was positive. He was diagnosed with Graves’ disease. Anti-thyroid medication was chosen as the initial treatment for Graves’ disease. However, this treatment failed to normalize the free triiodothyronine, free thyroxine, and thyroid stimulating hormone levels. His thyroid hormone levels indicated syndrome of inappropriate secretion of thyroid stimulating hormone. After cessation of methimazole treatment by remission of Graves’ disease, his state of syndrome of inappropriate secretion of thyroid stimulating hormone persisted. Magnetic resonance imaging revealed no pituitary tumor lesions. The results of thyroid stimulating hormone-releasing hormone stimulation test showed a normal response of thyroid stimulating hormone. He was suspected to have resistance to thyroid hormone. Direct sequencing analysis of the thyroid hormone receptor β gene identified a heterozygous missense mutation, R282S. Coexistence of resistance to thyroid hormone with Graves’ disease was confirmed. He has no signs of thyrotoxic symptoms, and is capable in activities of daily living at the present time. Conclusion We described a rare case of resistance to thyroid hormone simultaneously existing with Graves’ disease. This case demonstrated that these diseases can coexist, and indicated some of the difficulties in diagnosis of resistance to thyroid hormone with coexisting Graves’ disease. The diagnosis of resistance to thyroid hormone did not become apparent until after anti-hyperthyroidism treatment. Although rare, careful follow-up after the initial treatment of Graves’ disease is necessary. The coexistence of these two diseases should be considered in patients showing occasional syndrome of inappropriate secretion of thyroid stimulating hormone.

A rare mutation of thyroid hormone receptor beta gene in thyroid hormone resistance syndrome

Summary Resistance to thyroid hormone (RTH) is a rare hereditary syndrome with impaired sensitivity to thyroid hormones (TH) and reduced intracellular action of triiodothyronine (T3) caused by genetic variants of TH receptor beta (TRB) or alpha (TRA). RTH type beta (RTHβ) due to dominant negative variants in the TRB gene usually occurs with persistent elevation of circulating free TH, non-suppressed serum TSH levels responding to a thyrotropin-releasing hormone (TRH) test, an absence of typical symptoms of hyperthyroidism and goiter. Here, we present a rare variant in the TRB gene reported for the first time in an Italian patient with generalized RTHβ syndrome. The patient showed elevated TH, with non-suppressed TSH levels and underwent thyroid surgery two different times for multinodular goiter. The genetic test showed a heterozygous mutation in exon 9 of the TRB gene resulting in the replacement of threonine (ACG) with methionine (ATG) at codon 310 (p.M310T). RTHβ syndrome should be considered in patients with elevated TH, non-suppressed TSH levels and goiter. Learning points Resistance to thyroid hormone (RTH) is a rare autosomal dominant hereditary syndrome with impaired tissue responsiveness to thyroid hormones (TH). Diagnosis of RTH is usually based on the clinical finding of discrepant thyroid function tests and confirmed by a genetic test. RTH is a rare condition that must be considered for the management of patients with goiter, elevation of TH and non-suppressed serum TSH levels in order to avoid unnecessary treatments.