BONE-MINERAL DENSITY IN PATIENTS WITH ENDOGENOUS SUBCLINICAL HYPERTHYROIDISM - IS THIS THYROID STATUS A RISK FACTOR FOR OSTEOPOROSIS

OBJECTIVE The aim of the present study was to elucidate whether endoge nous subclinical hyperthyroidism due to a solitary autonomously functi oning thyroid nodule affects bone metabolism and is a risk factor lor osteoporosis. DESIGN In a cross-sectional study measurements of bone m ineral density were performed in premenopausal and post-menopausal wom en. Patients were categorized into non-toxic nodular goitre (n = 32), subclinical hyperthyroid (n = 37) and toxic solitary autonomous thyroi d nodule (n = 22) subgroups and the results were compared with those o f sex and age-matched control reference population (n = 68). MEASUREME NTS Lumbar spine and femoral neck bone mineral densities were measured by dual energy X-ray absorptiometry. Single-photon absorptiometry was applied to the measurement of bone mineral content in the midshaft of the radius. RESULTS In the non-toxic nodular goitre group, bone densi ties for all the scanned sites did not differ from the sex and age-mat ched reference population. At the L2-4 scanning site a significant dec rease in the bone mineral density could be observed only in the toxic nodular goitre group and this decrease was more marked in the postmeno pausal (P<0.001) than in the premenopausal females (P<0.05). At the fe moral neck and midshaft radius the mean densitometric values were slig htly, but significantly, lower only in the post-menopausal subclinical hyperthyroid group compared with the reference population (P<0.01). T he bone mineral density of the femoral neck, as well as the bone miner al content of the midshaft radius, was significantly decreased in both the premenopausal and post-menopausal patients with a toxic solitary nodule. CONCLUSION This study indicates that the bone mineral density of the lumbar spine, femoral neck and the midshaft of the radius are n ot significantly decreased in premenopausal patients with endogenous s ubclinical hyperthyroidism resulting from a solitary autonomously func tioning thyroid nodule. Conversely, findings hint at the possibility t hat long-lasting endogenous subclinical hyperthyroidism may be a contr ibuting factor to the development of osteoporosis in some post-menopau sal women, mostly at sites where cortical bone preponderates.