The insulin-like growth factor-I system and hormone replacement therapy

Objective: To determine the effects of hormone replacement therapy on plasm a concentrations of free and total insulin-like growth factor (IGF)-1, IGF binding protein (BP)-1, and IGFBP-3. Design: Clinical study. Setting: Gynecologic clinic at a university hospita l. Patient(s): Seventy-one postmenopausal women. Intervention(s): Six cycles of four different hormonal replacement therapy regimens: oral conjugated estrogens, transdermal estradiol, oral conjugated estrogens and norethisterone, and transdermal estradiol and norethisterone acetate. Main Outcome Measure(s): Blood samples were collected before and after trea tment for measurement of free and total IGF-1, IGFBP-1, and IGFBP-3. Result(s): Conjugated estrogen replacement therapy is associated with a dec rease in plasma concentration of total IGF-1 and increase in concentrations of free IGF-1 and IGFBP-1. Transdermal estrogens have no effect on total a nd free IGF-1 and IGFBP-1 concentrations. Oral norethisterone plus conjugat ed estrogens increased free IGF-1 and IGFBP-1 concentrations but did not ch ange IGF-1 concentrations. Transdermal conjugated estrogens plus norethiste rone acetate increased free IGF-1 concentrations but not total IGF-1 or IGF BP-1 concentrations. The plasma concentration of IGFBP-3 did not change in any group. Conclusion(s): Alterations in total IGF-1 concentration can occur depending on the route of hormone replacement therapy administration. Free IGF-1 con centrations were elevated in all study groups except that treated with tran sdermal estrogens. (C) 2001 by American Society for Reproductive Medicine.