Serum concentrations of somatomedins and growth hormone in relation to bone metabolism in acromegaly and thyroid dysfunction.

Many hormones are involved in the complex process of formation and resorption of bone. However, only somatomedin is found to directly stimulate cell replication and collagen synthesis in bone. This study was undertaken to examine a possible regulatory role of somatomedin in mediating the effects of growth hormone and thyroid hormones on bone metabolism. Bone metabolism and concentrations of somatomedins and growth hormones were studied in 17 acromegalic, 15 thyrotoxic and 14 hypothyroid patients, before and during treatment. During treatment of acromegalic and thyrotoxic patients parameters of bone turnover, both formation and resorption, decreased parallel to the decrease in concentration of somatomedin. During treatment of hypothyroid patients parameters of bone turnover increased. A positive correlation was found in acromegalic patients between changes in somatomedins and parameters of bone resorption (R = 0.82, P less than 0.01) as well as bone formation (R = 0.63, P less than 0.05) and in thyrotoxic patients between changes in somatomedin and bone resorption (R = 0.87, P less than 0.05). These data suggest that somatomedin may indeed play a role in the regulation of bone turnover. In addition, secondary effects on growth hormone concentrations were observed.