Changes in Sex Hormone-Binding Globulin Plasma Concentrations Induced by Body Weight and Estrogen Status in Perimenopausal Years

A cross-sectional study was conducted on 562 healthy perimenopausal women, with a mean age of 52.6 years, to follow perimenopausal changes in sex hormone-binding globulin (SHBG) plasma levels during the perimenopausal years. According to menstrual history and follicle-stimulating hormone (FSH) levels, 398 women were considered postmenopausal, and 164 were premenopausal. Women with a body mass index (BMI) of 25 were thought to be overweight. To study the effect of oral hormone replacement therapy, 153 women in the postmenopausal group were given 0.625 mg/day of oral conjugated estrogen plus medroxyprogesterone acetate, 10 mg/day, for 12 days every 3 months. SHBG levels were assayed at baseline and after 12 months of therapy. SHBG was positively associated with 17 β-estradiol plasma levels (r = 0.09, p < 0.05), and there was a strong negative correlation with BMI (r = −0.27, p < 0.001). After menopause, SHBG plasma levels dropped significantly (p < 0.05), but only in lean women. Similarly, hormone replacement therapy increased SHBG plasma levels in lean postmenopausal women (p < 0.001) but not among overweight treated women. These findings indicate that circulating estrogens are the main factor in SHBG metabolism in lean women, while obesity apparently abolishes the hormonal influence of ovarian estrogen and of hormone replacement therapy.