Body composition modulates the effects of hormone replacement therapy on growth hormone and insulin-like growth factor-I levels in postmenopausal women.

Objective: To examine the relationships of body composition with basal serum estrone, estradiol, androstenedione, cortisol, growth hormone (GH) and insulin-like growth factor-1 (IGF-1) levels in 73 postmenopausal women.

Design: Cross-sectional study of hormone levels and body composition determined by dual-energy X-ray absorptiometry and anthropometry in women who were not taking oral hormone replacement therapy (HRT) and women taking HRT. Because high adiposity may modify hormone levels, subjects were grouped by fatness into obese (BMI >25 kg/m(2) and waist circumference >80 cm) and lean groups, as well as by HRT use.

Results: Total levels of estrone, estradiol, GH and cortisol were significantly higher and IGF-1 was lower in HRT users. In HRT users, estradiol levels were higher and GH levels were lower in obese than lean women. IGF-1 levels were lower in obese HRT users than lean nonusers. Total cortisol levels were significantly higher in lean HRT users than lean nonusers and obese users. GH and IGF-1 were significantly inversely correlated with trunk fat and percent body fat. Multiple regression revealed that only trunk fat was a significant (negative) determinant of GH and IGF-1 levels, whereas HRT use positively and negatively predicted GH and IGF-1, respectively. Percent body fat significantly predicted estradiol levels. Body composition did not differ by HRT use.

Conclusions: Our results suggest that trunk fat attenuates the HRT-induced increase on GH levels. In addition, trunk fat is a significant determinant of low IGF-1 levels in postmenopausal women, and IGF-1 levels decline more with HRT use.