Associations between brain-derived neurotrophic factor and estradiol in women's saliva.

OBJECTIVE: The aim of this study was to assess the relationship between brain-derived neurotrophic factor (BDNF) and sex hormones (estradiol [E2] and progesterone), using saliva samples obtained from healthy women.

METHODS: Forty female dental hygienist students were divided into groups according to being in the follicular phase or luteal phase. Saliva BDNF, E2, and progesterone levels were measured using a sandwich ELISA system. The correlation between these factors was analyzed using Spearman's index, and fluctuations of these levels in the whole menstrual cycle were investigated classifying the subjects by every 4 days according to the phase of their menstrual cycle.

RESULTS: Saliva BDNF variations strongly correlated with saliva E2 levels in the follicular phase (r = 0.721, p = 0.000) and luteal phase (r = 0.770, p = 0.000). The correlation coefficient showing the relationship between progesterone and BDNF levels in the luteal phase (r = 0.371, p = 0.157) was lower than that in the follicular phase (r = 0.631, p = 0.001). Moreover, the fluctuation of BDNF levels in the menstrual cycle followed a similar pattern to that of E2.

CONCLUSIONS: We found that saliva BDNF and E2 levels were closely related in healthy young women. In particular, for first time, that correlation was investigated throughout the menstrual cycle. Monitoring of saliva BDNF may yield insight into women's reproductive and mental health.