BONE MASS, BONE TURNOVER, BODY-COMPOSITION, AND CALCIUM HOMEOSTASIS IN FORMER HYPERTHYROID PATIENTS TREATED BY COMBINED MEDICAL THERAPY

It is still uncertain whether bone mass and bone turnover are complete ly normalized after treatment of hyperthyroidism. The aim of the prese nt investigation was to determine bone mass, bone turnover, body compo sition, and calcium homeostasis in former hyperthyroid patients who ha d been euthyroid for at least 4 years following combined medical thera py. Thirty-nine former hyperthyroid patients and 67 normal sex- and ag e-matched controls participated. Height, body weight, and body composi tion were similar in the two groups. All patients were euthyroid. Howe ver, serum FT3I (free T-3-index) was reduced by 9% (p < 0.01) in the p atients compared to controls, serum FT4I was normal, while serum TSH w as nonsignificantly reduced by 39%. No significant differences were ob served between patients and controls with respect to total or regional bone mineral content (BMC) or density (BMD). The former hyperthyroid patients had slightly higher serum calcium (2.35 +/- 0.06 vs. 2.32 +/- 0.07 mmol/L, p < 0.05) and lower serum phosphate (1.15 +/- 0.15 vs. 1 .24 +/- 0.15 mmol/L, p < 0.01) than their controls. Renal excretion of calcium and serum levels of magnesium, 1,25-vitamin D and intact PTH were unchanged. Renal excretion of pyridinoline was increased by 30% ( p < 0.05) in the patients, whereas the remaining resorptive markers, r enal excretion of hydroxyproline and deoxypyridinoline and serum cross -linked carboxy-terminal teleopeptide of type I collagen (ICTP) were u naltered. Among the formative bone markers the average serum carboxy-t erminal propeptide of human type I procollagen (PICP) level was 12% lo wer (p < 0.05) than in the control group, whereas serum levels of oste ocalcin and total and bone alkaline phosphatase were normal. In conclu sion, former hyperthyroid patients treated by combined medical therapy have normal bone mineral content and density in spite of minor variat ions in thyroid hormones and skeletal homeostasis.