NEW YORK (Reuters Health) - Findings from a new study suggest that estrogen as well as testosterone plan a crucial role in regulating bone resorption in men.

It is well known that declining estrogen levels put postmenopausal women at increased risk for osteoporosis. In contrast, the role of estrogen in men's bone health is less clear.

Previously, experts believed that testosterone was the dominant hormone for regulating bone growth in men. But a growing amount of research suggests that estrogen plays a key role.

Now, new findings published in the January issue of The Journal of Clinical Endocrinology suggest that both estrogen and testosterone are important independent regulators of bone turnover in men.

Lead author Dr. Benjamin Z. Leder and colleagues conducted a 12-week study of 70 healthy men between 20 and 44 years of age. The men had their hormone levels suppressed with medical therapy, and were then divided into one of three groups.

The hormones were replaced so that men had low levels of both testosterone and estrogen, normal levels of both hormones, or estrogen deficiency and normal testosterone levels. The researchers then measured several biochemical markers of bone turnover.

The most profound impact on bone turnover was noted in men who had both estrogen and testosterone levels suppressed. However, an effect was still observed in men who only had their estrogen levels suppressed.

The results suggest that testosterone and estrogen are "independent mediators of bone resorption in young adult men," Dr. Leder, who is with Northern General Hospital in Sheffield, England, and colleagues write.

"Although quantifying the effects of each hormone is not possible in the present study, the importance of both androgens and estrogens needs to be considered when assessing the effects of all hormonal therapies or manipulations in men," they add.

J Clin Endocrinol Metab 2003;88:204-210.

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