Insulin-like growth factor 1 and bone turnover in glucocorticoid-treated and control subjects

The role of the growth hormone-somatomedin axis in the genesis of steroid osteoporosis has been studied by measuring circulating insulin-like growth factor 1 (IGF-1) levels in asthmatic subjects either receiving or not receiving therapy with oral glucocorticoids. There was no difference in IGF-1 levels between the two groups (60.6 micrograms/l (95% confidence interval 47.3-77.8) in the control subjects vs 69.1 micrograms/l (49.3-96.9) in the steroid-treated group). IGF-1 declined with age in the control subjects but not in those taking steroids. When IGF-1 levels were correlated with biochemical indices of bone turnover, a significant relationship was found with urine hydroxyproline in the control subjects (r = 0.55, P less than 0.02) but not in those taking steroids. It is concluded that glucocorticoid therapy does not alter mean circulating levels of IGF-1 but that the growth hormone-somatomedin axis may influence bone turnover in normal subjects. Interference by glucocorticoids with the normal regulation of IGF-1 and its influence on bone turnover is suggested.