Although many people think of testosterone as a hormone exclusive to men, women need it too or else abnormalities in bone structure and body composition can occur.

Testosterone replacement has been shown to improve bone thickness, muscle mass, mood, and libido in androgen-deficient men, the authors explain, but little is known about the effects of testosterone replacement in androgen-deficient women.

Dr. K. K. Miller and colleagues, from Massachusetts General Hospital in Boston, investigated the effects of 12 months of testosterone replacement in 51 women of reproductive age with androgen deficiency due to disturbances in the pituitary gland, a tiny gland found in the brain. The participants were randomly assigned to receive either two testosterone patches or two fake "placebo" patches, changed twice weekly.

Testosterone levels increased into the normal range in women treated with testosterone, the authors report, whereas other hormone levels did not change.

Bone thickness at the hip and forearm increased significantly, the results indicate, although there was no change in spine bone thickness in women treated with testosterone compared with placebo.

Muscle area increased significantly in women treated with testosterone, the researchers note, but there was no change in fat area.

Women treated with testosterone experienced improvements in mood and sexual function and in quality-of-life, the investigators say. Testosterone treatment was associated with an increased incidence of acne, but there were no other differences in side effects between the testosterone and placebo groups.

While the results are encouraging, "further studies will be needed to determine long-term efficacy and safety of such a replacement strategy," the authors note.

SOURCE: Journal of Clinical Endocrinology and Metabolism, May 2006.