Endocrine Abstracts

Thyroid hormone resistance is a rare but recognised cause of clinical hypothyroidism. We explain a case of clinical hypothyroidism that was associated with thyroid hormone resistance.

A 48-year Caucasian female with no known personal or family endocrine history was referred with a 12-month-history of weight gain and increased tiredness. Past history included depression and osteoarthritis, with regular medications being NSAIDs and amitryptiline. There was no history of investigations with iodinated contrast, recent viral illnesses or amiodarone. Initial thyroid function tests-TSH 5.3 (0.2–6), T₄ 31.1(10–20) pmol/l. There was no evidence of heterophile antibody interference after polyethylene glycol precipitation tests. Similarly, repeating thyroid function tests after equilibrium dialysis (DELFIA TFT) did not alter the readings. Serum sex hormone binding globulin concentration was normal 47 (normal range 20–100) nmol/l suggesting TSHoma unlikely. Sample sent for thyroid hormione receptor gene mutation screening – heterozygous for THRB C.1313G>A single base change mutation (Arg 438 His). Patient referred to the local clinical genetics service for family screening. Commenced on 25 μg of levothyroxine with a view to alleviate symptoms.

Conclusion: Clinical hypothyroidism with elevated TFTs should suggest the possibility of thyroid hormone resistance and be investigated accordingly.