Thyroid hormone resistance differential — SCE Endocrinology MCQ

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HardThyroidThyroid hormone resistance differentialSCE Endocrinology

A 26-year-old man is screened because his mother has abnormal thyroid tests. He is clinically well. Free T4 and free T3 are raised on two platforms, TSH is 3.2 mU/L, alpha-subunit is normal and pituitary MRI is normal. What is the most likely diagnosis?

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Correct answer: C — Resistance to thyroid hormone beta

Resistance to thyroid hormone beta is best because raised thyroid hormones with non-suppressed TSH, normal alpha-subunit and family history supports resistance to thyroid hormone beta. The alternatives are less appropriate because Graves' and factitious thyrotoxicosis suppress TSH; TSHoma often has pituitary lesion or raised alpha-subunit; primary hypothyroidism has low thyroid hormone. The SCE teaching point is to integrate the clinical pattern, biochemistry and context rather than treating an isolated result.

Reference: European Thyroid Association central hyperthyroidism guidance