The IGF-system in healthy pre- and postmenopausal women: relations to demographic variables and sex-steroids

Plasma insulin-like growth factor (IGF)-I, free IGF-I and -II, IGF-binding protein (IGFBP)-1, -2, and -3 together with IGFBP-3 protease activity were measured in 114 postmenopausal and 39 premenopausal healthy women. For each parameter, the mathematical distribution was characterised, and the normal range for pre- and postmenopausal women described, together with correlations to demographic variables and sex-steroids (postmenopausal women). Postmenopausal women had lower levels of plasma IGF-I (P < 0.001) and free IGF-I (P < 0.001) compared to premenopausal women, while plasma IGFBP-2 (P < 0.05) and immunoreactive IGFBP-3 (P < 0.001) were higher in postmenopausal women. Free IGF-I (but none of the other parameters) was significantly lower in postmenopausal smokers compared to non-smokers (P < 0.05). IGF-I and -II both correlated positively to height (r = 0.203, P < 0.05 and r = 0.198, P < 0.05, respectively), while IGF-II correlated positively to weight (r = 0.250, P < 0.01). Plasma IGF-I correlated positively to androstenedione (r = 0.292, P < 0.01) and dehydroepiandrosterone sulphate (DHEAS, r = 0.202, P < 0.05), while a significant positive correlation was observed between IGF-II on the one side and oestradiol (E-2, r = 0.227), oestrone sulphate (E1S, r = 0.238) and androstenedione (r = 0.213) on the other side (P < 0.05 for all). Our results support a relation between sex-steroids and IGF-I and -II in healthy postmenopausal women. The lower levels of total and free IGF-I in postmenopausal compared to premenopausal women indicate lower bioavailability of this growth factor in elderly females. (C) 2002 Published by Elsevier Science Ltd.