[Lotus]

This study is interesting, and although free estradiol is difficult to determine I wonder how the bioavailability of free E would alter the outcome.


Total estradiol, rather than testosterone levels, predicts osteoporosis in aging men.

Abstract
OBJECTIVE:
To study and establish sex hormone cutoff levels for osteoporosis risk in men over 50 years old.

METHODS:
Case-control study of 216 men > 50 years, 110 with osteoporosis (O) and 106 with normal bone density ©. We measured estradiol (E2), sex hormone binding globulin (SHBG), total testosterone (TT) and albumin. Free testosterone (FT) and bioavailable testosterone (BT) were calculated through Vermeulen's formula.

RESULTS:
There was no difference in TT between groups. Relative risks of osteoporosis were 1.89 for E2 < 37 pg/mL (p = 0.02); 1.91 for SHBG > 55 nmol/L (p = 0.019); 2.5 for FT < 7 ng/dL (p = 0.015); 2.7 for BT < 180 ng/dL (p = 0.0003).

CONCLUSIONS:
In men over 50 years old, TT was not indicative of osteoporosis risk while E2 < 37 ng/mL was. SHBG > 55 nmol/L, FT < 7 ng/dL and BT < 180 ng/dL can represent additional indications for osteoporosis screening in men over 50 years old.

http://www.ncbi.nlm.nih.gov/pubmed/20126856#