IDENTIFICATION OF METABOLIC BONE-DISEASE IN PATIENTS WITH ENDOGENOUS HYPERTHYROIDISM - ROLE OF BIOLOGICAL MARKERS OF BONE TURNOVER

Active hyperthyroidism is associated with reduced bone mass. Neverthel ess, not all patients show the same risk for developing osteoporosis. Our aim was to analyze some clinical and biochemical potential predict ors of low bone mass in hyperthyroid patients. We studied 127 consecut ive hyperthyroid patients (110 females, 17 males; aged 42 +/- 16 years ). Bone mineral density (BMD) was measured by dual X-ray absorptiometr y (DXA) at lumbar spine (LS; L-2-L-4) and femoral neck (FN). Data were expressed as g/cm(2) and T-score. Patients were placed into two group s based on recent WHO criteria: Group A, no osteoporosis (n = 98); and group B, lumbar or femoral osteoporosis (n = 29). Study protocol incl uded evaluation of osteoporosis risk factors, anthropometrical variabl es, thyroid function, and bone turnover markers. Receiver-operating ch aracteristic (ROC) plots for the precision of bone markers and multiva riate analysis for the prediction of BMD and osteoporosis were perform ed. Group B showed greater age and proportion of menopausal females; l ower weight, height, and calcium intake; longer duration of menopause; and greater levels of total and bone alkaline phosphatase and of urin e hydroxyproline. No differences in thyroid function, osteocalcin, tar trate-resistant acid phosphatase, and type I collagen C-telopeptide (I CTP) were found. The best predictive model accounted for 46% and 62% o f the variability of lumbar and femoral BMD respectively and correctly classified 89% of the osteoporotic hyperthyroid patients. No signific ant difference in ROC plots was observed. It is concluded that hyperth yroid patients with lumbar or femoral osteoporosis show a typical clin ical and biochemical profile illustrating that the relationship betwee n BMD and bone markers is better in high turnover states. Classical bo ne turnover markers show high performance in the evaluation of hyperth yroid bone disease.