Endocrine & metabolic · UKMLA & AKT
Drug-induced and factitious thyrotoxicosis
A free high-yield preview for the UKMLA Applied Knowledge Test, covering how to recognise this condition. The full SA Note notes add investigations, management and complications, with practice questions on this topic.
Key high-yield points
- Beta-hCG and TSH share identical alpha subunits - at very high concentrations (e.g. molar pregnancy), beta-hCG cross-reacts with TSH receptors on thyroid follicular cells, stimulating T4/T3 production
- Elevated T4/T3 exerts negative feedback on the pituitary → suppressed TSH
- Result: high beta-hCG + low TSH + high thyroxine - the expected pattern in gestational trophoblastic disease (hydatidiform mole)
Molar pregnancy = very high beta-hCG → TSH receptor stimulation → thyrotoxicosis. TFTs show suppressed TSH + elevated FT4/FT3. Definitive treatment is uterine evacuation.
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