BONE METABOLISM DURING ANTITHYROID DRUG-TREATMENT OF ENDOGENOUS SUBCLINICAL HYPERTHYROIDISM

OBJECTIVE There is recent evidence that both exogenous and endogenous subclinical thyrotoxicoses are associated with decreased bone mineral density. Scanty information is available on bone metabolism in these c onditions when euthyroidism is restored. We evaluated the effect of an ti-thyroid drug treatment on bone metabolism in endogenous subclinical hyperthyroidism. DESIGN Prospective follow-up study over 2 years duri ng treatment with methimazole, with an untreated control group. SUBJEC TS Sixteen post-menopausal women with endogenous subclinical hyperthyr oidism associated with multinodular goitre, eight of whom were treated with methimazole. MEASUREMENTS Serum concentrations of free T4, total T3, TSH, osteocalcin, urinary excretion of hydroxyproline and forearm bone mineral density were measured at regular intervals. RESULTS Sign ificant changes in serum osteocalcin concentration or urinary hydroxyp roline excretion were not observed in either group. Distal, but not pr oximal, forearm bone mineral density, expressed as a percentage of the base-line value, was significantly (P < 0.05) higher in the treated t han in the untreated subjects in the second year of treatment. CONCLUS ION Treatment with methimazole in postmenopausal women with endogenous subclinical hyperthyroidism associated with multinodular goitre can p revent excessive loss of bone, at least in the distal forearm.