Effects of HRT on serum levels of IGF-I in postmenopausal women

Abstract

Objectives: It is thought that insulin-like growth factor-1 (IGF-I) stimulates bone formation. We aimed to determine the effects of oral and transdermal hormone replacement therapy (HRT) on serum IGF-I levels and to investigate the effects of basal IGF-I levels on the levels obtained at the end of the therapy. Methods: Sixty-six postmenopausal women were administered either oral ( n=44) or transdermal ( n=22) HRT for 6 months. Serum levels of IGF-I were determined before and after HRT in all subjects. Groups were divided into two subgroups according to the median value of serum IGF-I levels (basal IGF-I levels above or below the median value). The increase of IGF-I levels after HRT were calculated (%) for all women. Mean increases of subgroups were compared. Furthermore, study groups were divided into three subgroups according to the changing of IGF-I (increase>25%, between 25% increase and 25% decrease and decrease>25%). Mean basal IGF-I levels of these three subgroups were compared. Results: Mean serum levels of IGF-I before and after HRT were not significantly different in both oral and transdermal groups ( P>0.05). Mean increases of IGF-I after HRT for the patients with low basal IGF-I levels, were 65% in oral and 77% in transdermal groups. However, mean increase of the patients with high basal IGF-I levels were −8 and −16% respectively. Moreover, mean level of basal IGF-I was significantly low in women who have more than a 25% increase after HRT ( P<0.05). Conclusion: HRT seems to significantly increase serum levels of IGF-I in postmenopausal women with low basal levels of IGF-I.