Endocrine Abstracts

With age, sex hormones concentrations undergo changes but may continue to have a significant impact: several studies have shown the association of low levels of bioavailable estradiol (BE2) with osteoporosis in man. In postmenopausal women, estradiol levels may influence cognitive function or breast cancer risk.

A better approach of sex hormones profiles related to age becomes necessary. We evaluated BE2 concentrations and its variation with age in men, and in postmenopausal women.

Methods: Serum from 183 patients from an endocrinology department: 142 men (15–83) year old, and 41 postmenopausal women, were analysed for measurement of estradiol and BE2. Serum of men were chosen with normal testosterone and bioavailable testosterone (BT) concentrations.

Estradiol concentrations were assayed with a solid-phase RIA (Diasorin) without extraction. Testosterone was measured after extraction using with a solid-phase RIA (IDS). BT and BE2 were obtained after serum equilibration with tritiated hormones, by ammonium sulfate precipitation of SHBG-bound steroid and by the calculation as the product of percentage non-SHBG bound and total estradiol or testosterone concentration.

Results: Total testosterone, BT and BE2 significantly decrease with age (Spearman: P 0.035, <0.0001, <0.0001, respectively) as total estradiol does not significantly change (see Table median (5 and 95%)).

In postmenopausal women median BE2 was16 (8–29) pmol/l.

Conclusion: A BE2 concentration <13 pmol/l in older men (and <8 pmol/l in postmenopausal women) can be considered low. Whether this may constitute a threshold value to be taken into account for assessment of a risk for osteoporosis (or dementia in women) remains to be determined.