Associations of Estrogen and Testosterone With Insulin Resistance in Pre- and Postmenopausal Women With and Without Hormone Therapy

BACKGROUND: Estrogen deficiency due to natural menopause or surgical menopause has been suggested to have an adverse effect on insulin resistance. Testosterone and sex hormone–binding globulin (SHBG) as well as estrogen are also associated with insulin resistance in women. However, to date, the associations of estradiol, testosterone and SHBG with insulin resistance according to estrogen level have not been clarified. OBJECTIVES: We examined the associations of estradiol, testosterone and SHBG with insulin resistance in pre- and in postmenopausal women and postmenopausal women who had received hormone therapy to clarify whether the associations differ depending on the estrogen status. PATIENTS AND METHODS: Twenty premenopausal women and thirty-two postmenopausal women were enrolled in this study. Fifteen postmenopausal women received oral conjugated equine estrogen (CEE) (0.625 mg) everyday for 12 months. Serum levels of estradiol, testosterone, SHBG and insulin and plasma levels of glucose were measured. RESULTS: Serum estradiol levels tended to have a negative correlation with homeostasis model assessment of insulin resistance (HOMA-IR) in premenopausal women but not in postmenopausal women. On the other hand, free testosterone levels tended to have a positive correlation with HOMA-IR in postmenopausal women but not in premenopausal women. Serum SHBG levels showed significant negative correlations with HOMA-IR in both pre- and postmenopausal women. SHBG level was significantly increased, free testosterone level was significantly decreased and HOMA-IR was significantly decreased at 12 months after CEE administration. However, there were no significant correlations of changes between estradiol, SHBG or free testosterone and HOMA-IR. CONCLUSIONS: The associations of sex steroid hormones with insulin resistance are different depending on the estrogen status.