Influence of endogenous and exogenous sex hormones on plasma brain-derived neurotrophic factor

Brain-derived neurotrophic factor (BDNF) is a mediator of neuronal plasticity and influenceslearning, memory and cognitive behaviour. The aim of this study is to assess plasma BDNF variations according tohormonal status. METHODS: A total of 60 subjects were included: 20 fertile ovulatory women, 15 amenorrhoeicwomen and 25 postmenopausal women. Blood samples were collected after overnight fasting. For 5 out of the 20fertile women, samples were collected every 2 days throughout the whole menstrual cycle. Following basal evaluation,10 out of 25 postmenopausal women were administered a hormone replacement therapy (HRT) and reevaluated after6 months of treatment. Plasma BDNF concentrations were measured by enzyme-linked immunosorbent assay. Infertile women, estradiol (E2), progesterone and gonadotrophins were also assessed. RESULTS: In fertile women,luteal phase levels of plasma BDNF were significantly higher than follicular phase levels (P < 0.001). BDNF increasedfrom early follicular phase up to Day 14 of the cycle, reaching a pre-ovulatory peak, similar to E2. A second rise tookplace during mid-luteal phase, with a peak on Day 24. Amenorrhoeic subjects, as well as postmenopausal women,showed significantly lower plasma BDNF levels compared with fertile females (P < 0.001). BDNF was positively correlatedwith E2 and progesterone and negatively correlated with menopausal age. HRT restored BDNF levels to thosepresent in fertile women during the follicular phase. CONCLUSIONS: Plasma BDNF levels are influenced by hormonalstatus. Modifications in BDNF circulating levels during the menstrual cycle suggest a potential role for gonadal sexhormones (E2 and progesterone) in regulating neurotrophin expression.