Oestradiol plus progesterone treatment increases serum leptin concentrations in normal women

BACKGROUND: Previous studies have alluded to a role for both oestradiol and progesterone in the secretion of leptin from fat cells in the human, altho ugh direct evidence has yet to be obtained. The study aim was to assess ser um leptin concentrations in normally cycling women receiving exogenous oest radiol and progesterone. METHODS: Normally cycling women were investigated in an untreated spontaneous cycle (control, n = 10), a cycle treated with o estradiol (oestradiol cycle, n = 10) and a cycle treated with oestradiol pl us progesterone (oestradiol + progesterone cycle, n = 6). Oestradiol was gi ven to the women through skin patches on cycle days 2, 3 and 4, and progest erone intravaginally on cycle days 3, 4 and 5. Serum concentrations of lept in, oestradiol, progesterone, FSH and LH were measured in daily blood sampl es. RESULTS: During the treatment, serum oestradiol and progesterone concen trations increased significantly. In the oestradiol cycles, leptin concentr ations were not affected by treatment and did not differ from those in cont rols. In the oestradiol+progesterone cycles, leptin concentrations (mean +/ - SEM) increased in all women from cycle day 3 (8.6 +/- 1.1 ng/ml) to days 5 (12.2 +/- 1.8 ng/ml, P < 0.01) and 6 (11.9 +/- 2.0, P < 0.05), and were a t these points significantly higher than in the control cycles (P < 0.05). The mean percentage increase from day 3 to the peak concentration on days 5 or 6 was 62.6 +/- 6.8%. Leptin concentrations returned to the pretreatment value on day 7, together with the concentrations of oestradiol and progest erone. In the oestradiol+progesterone cycles, leptin concentrations correla ted significantly with oestradiol and progesterone concentrations, but not with FSH and LH concentrations. CONCLUSIONS: These results show, for the fi rst time, that leptin secretion can be stimulated in women by the administr ation of oestradiol plus progesterone. This may explain the increased conce ntrations of leptin during the luteal phase of the normal menstrual cycle.