Effect of hormone replacement therapy and tibolone on serum leptin levels in postmenopausal women.

Objective: To evaluate the effect of estrogen replacement therapy (ERT), continuous combined hormone replacement therapy (HRT) and tibolone on serum leptin levels in healthy postmenopausal women.

Methods: Eighty-four healthy postmenopausal women aged 43-63 years were studied prospectively. Hysterectomized women (n = 16) received conjugated equine estrogens (CEE) 0.625 mg. Women with an intact uterus were randomly allocated either to CEE+medroxyprogesterone acetate (CEE/MPA) 5 mg or tibolone 2.5 mg. Serum leptin levels were assessed at baseline and after 6 months of treatment.

Results: The three groups did not differ with respect to age, body mass index (BMI) or baseline serum leptin levels. Overweight women (BMI > 25 kg/m2) had higher baseline leptin levels (27.0 +/- 11.4 ng/ml) compared to their lean counterparts (BMI < or = 25 kg/m2; leptin: 16.5 +/- 8.1 ng/ml, P = 0.0001). Neither CEE nor CEE/MPA had any effect on serum leptin levels at the end of 6 months either in overweight or in lean women (overweight: CEE baseline 34.4 +/- 13.3 ng/ml, 6 months 36.9 +/- 15.8, P = 0.89, CEE/MPA baseline 22.4 +/- 9.8 ng/ml, 6 months 26.8 +/- 8.7 ng/ml, P = 0.1; lean: CEE baseline 12.6 +/- 4.4 ng/ml, 6 months 13.2 +/- 5.8 ng/ml, P = 0.36, CEE/MPA baseline 17.2 +/- 10.6 ng/ml, 6 months 18.8 +/- 8.8 ng/ml, P = 0.31). Similarly serum leptin remained unchanged at the end of the study in both lean and overweight women on tibolone (overweight: baseline 22.9 +/- 8.1 ng/ml, 6 months 18.5 +/- 12 ng/ml, P = 0.37; lean: baseline 13.2 +/- 5.6 ng/ml, 6 months 17.3 +/- 8.4 ng/ml).

Conclusion: BMI is a strong determinant of serum leptin levels in healthy postmenopausal women. Neither ERT/HRT nor tibolone exert any effect on serum leptin after 6 months in lean or overweight postmenopausal women. Further studies are required to verify the exact role of estrogen and tibolone on leptin production and function in postmenopausal women.