Objective: Leptin. a protein secreted by white adipocytes, plays a relevant role in the regulation of body weight and food intake. A possible role for sex hormones in the regulation of leptin secretion has been suggested; however, the effect of variations in oestrogen concentration on serum leptin levels has not been described so far.
Methods: In study 1, serum leptin concentrations were measured on days 3, 10, 17 and 24 of the menstrual cycle in 18 healthy, lean, regularly menstruating women, aged 18-35 years. Serum oestradiol, progesterone, testosterone. Delta4-androstenedione, dehydroepiandrosterone sulphate (DHEAS). LH and FSH concentrations were also determined. In study 2, serum leptin and oestradiol levels were measured on the 5th and 7th day of ovarian stimulation with human FSH (225 IU daily) during an in vitro fertilisation programme for infertility in 20 women aged 25-45 years.
Results: The results from study 1 show a physiological fluctuation of leptin levels during the menstrual cycle, which has not been described previously. Leptin levels are significantly lower in the early follicular phase. The results of study 2 show a parallel increase in serum oestrogen and leptin concentrations during FSH administration.
Conclusions: The fluctuation in leptin levels during the menstrual cycle observed in study 1 is compatible with the hypothesis of a stimulatory effect of oestrogen on leptin secretion. The results of study 2 support the hypothesis of a relevant role for oestrogen in the regulation of leptin secretion. Leptin fluctuations during the menstrual cycle are consistent with reported perimenstrual variations in food craving and consumption.