Hormonal regulation of serum lipoprotein(a) levels: Contrasting effects of growth hormone and insulin-like growth factor-I

In response to treatment with growth hormone, serum levels of lipoprotein(a) increase, while those of LDL cholesterol decrease. To establish if increased levels of insulin-like growth factor-I may be of importance for these changes, we analyzed serum lipoprotein concentrations in II male patients with idiopathic osteoporosis who were treated with growth hormone (2 IU · m^-2 · d^-1) or insulin-like growth factor-I (80 μg · kg^-1 · d^-1) in a randomized, double-blind, cross-over study. LDL cholesterol was reduced by 0.7 mmol/L (P<.01) during growth hormone treatment but was not affected when the same patients received insulin-like growth factor-I. In contrast, mean lipoprotein(a) levels increased from 519 to 571 mg/L (P<.03) in response to growth hormone but were reduced from 538 to 478 mg/L (P<.04) during treatment with insulin-like growth factor-I. These results indicate that growth hormone exerts its effects on lipoprotein metabolism independent of insulin-like growth factor-I. Furthermore, the results suggest that treatment with insulin-like growth factor-I may reduce lipoprotein(a) levels.