Short-term effects of recombinant human insulin-like growth factor I on bone turnover in normal women

Because insulin-like growth factor I (IGF-I) is a potent stimulator of osteoblast proliferation, it has potential in the treatment of osteoporosis. However, IGF-I affects multiple organ systems, and it is unclear whether treatment can stimulate bone formation without producing unacceptable side effects. Therefore, we evaluated the effects of treatment with recombinant human IGF-I in 18 postmenopausal women who received various dosages (30, 60, 120, or 180 micrograms/kg.day) by sc injections for 6 days. Serum IGF-I concentrations increased by 2- to 4-fold during treatment. There were dose-dependent increases in serum type I procollagen carboxyl-terminal propeptide concentration (r = 0.85, P < 0.001), an index of collagen synthesis, and of urinary excretion of deoxypyridinoline (r = 0.75, P = 0.001), an index of bone collagen breakdown. At the two higher dosages, recombinant human IGF-I caused orthostatic hypotension, sinus tachycardia, bilateral parotid discomfort, weight gain, and edema in some women. Hypoglycemia did not occur. However, treatment at the 2 lower dosages increased serum type I procollagen carboxyl-terminal propeptide significantly and produced minimal or no side effects. Long-term studies on the effects and the safety of low dosage recombinant human IGF-I on bone mass should now be undertaken in osteoporotic women.