Plasma insulin-like growth factor-I and its binding proteins 1 and 3 during continuous nonoral and oral combined hormone replacement therapy

Objective: We determined the effects of continuous combined nonoral and ora l estrogen-progestin therapy on plasma levels of insulin-like growth factor -I (IGF-I) and its binding proteins 1 (IGFBP-1) and 3 (IGFBP-3), Design: Forty women complaining of climacteric symptoms were randomized to receive either transdermal estradiol patches (50 mu g daily) in combination with an intrauterine system releasing 20 mu g of levonorgestrel daily or a n established regimen of an oral dose of 2 mg of estradiol and 1 mg of nore thisterone acetate daily for 1 year. Fifteen women in the nonoral therapy g roup and 17 in the oral therapy group completed the 1-year prospective stud y. Results: Plasma levels of IGF-I decreased significantly in the oral therapy group, but no changes were observed in the plasma levels of its binding pr oteins. Transdermal estrogen in combination with intrauterine levonorgestre l did not induce any change in plasma IGF-I, whereas the plasma levels of I GFBP-3 decreased. IGFBP-1 concentrations increased, which may be related to the induction of this protein into the endometrium by the intrauterine lev onorgestrel delivery. Conclusions: Both the nonoral and oral continuous combined estrogen-progest in therapies used in this study produced only minor changes in the circulat ing concentrations of IGF-I and its binding proteins. (Menopause 1998;5:217 -222, (C) 1998, The North American Menopause Society.).