Age, BMI determined serum levels of estrogen, SHBG among HT users

Overweight and obese postmenopausal women assigned to estradiol therapy attained greater estrogen concentrations but lower sex hormone-binding globulin levels compared with normal-weight women in a new study.

To examine the estrogen concentrations of older, heavier women, researchers measured serum levels of estrogen, total and free estradiol and SHBG for 91 women randomly assigned to 1 mg oral micronized 17beta-estradiol and 89 assigned to placebo; all were included in the Estrogen in the Prevention of Atherosclerosis Trial.

During two years of treatment, six-month measurements revealed that total (P=.01) and free estradiol (P=.002) were significantly associated with BMI adjusted for age among estradiol users. SHBG levels were inversely related to waist-to-hip ratio adjusted for age (P=.005).

Analyses revealed no association of age with estrogen or SHBG concentrations among women assigned to estradiol or placebo.

BMI was positively associated with estrone concentrations among estradiol users aged 65 years and older (P=.03), and older, obese HT users had the highest concentrations.

“It may be useful to consider age and obesity when prescribing HT to minimize the risk of venous thrombosis or stroke in postmenopausal women,” the researchers concluded. “Further research regarding relationships among circulating hormone levels and risk for these conditions is required to substantiate this conclusion.”

Karim R. J Clin Endocrinol Metab. 2009;94:4136–4143.