Treatment with the synthetic hormone tibolone is associated with a decrease in body fat and leptin levels in postmenopausal women, according to study results published in the journal Fertility and Sterility for February.

Dr. Mithat Erenus, of Marmara University Hospital in Istanbul, Turkey, and colleagues randomly assigned 120 healthy postmenopausal to combined conjugated estrogen 0.625 mg plus medroxyprogesterone acetate 2.5 mg (Premelle 2.5; Wyeth-Ayerst), tibolone 2.5 mg (Livial; Organon), or to a comparison or "control" group for 6 months.

"The serum leptin levels were in strong correlation with the total fat percentage and total fat mass at baseline," the investigators report.

After 6 months, women in the control group had gained weight, with a gradual decrease in leptin levels. Leptin is natural hormone that regulates fat metabolism. This may explain the tendency of women to accumulate visceral after menopause.

Conventional hormone therapy "reversed this negative effect of menopause by increasing leptin while maintaining body weight, and mostly in the fat distribution."

In contrast, women in the tibolone group "had a significant decrease in leptin levels accompanied by decreased total fat mass, fat percentage, and increased total lean mass."

However, Erenus and colleagues note that the study did not include information on growth hormone levels, or physical activity "that may have an impact on weight gain in postmenopausal women."