Serum kisspeptin levels across different phases of the menstrual cycle and their correlation with serum oestradiol

Objective: A rise in oestrogen in the preovulatory phase produces a GnRH-induced luteinising hormone surge. Oestrogen receptors are not found on GnRH neurons but these are present on kisspeptin neurons. That led us to hypothesise that serum kisspeptin levels may vary during various phases of the menstrual cycle in relation to serum oestradiol. Methods: Thirty female students, 18-25 years old, Saudi nationality, with a regular menstrual cycle, were recruited from various health colleges of the University of Dammam, Saudi Arabia. Three blood samples per volunteer were collected at three different times: the early follicular, preovulatory and luteal phase. Serum kisspeptin and oestradiol were measured using ELISA kits. Comparison between individual subjects during the various phases was done by one-way, repeated-measures ANOVA. To discover which specific means differed, Bonferroni post hoc test was applied. Pearson's correlation was used to find out the relationship. Results: There was a statistically significant increase (p < 0.001) in serum kisspeptin levels from the early follicular to the preovulatory phase (264.11 +/- 28.42 vs. 472.46 +/- 17.82 nmol/l respectively), and from the preovulatory to the luteal phase (472.46 +/- 17.82 vs. 724.79 +/- 36.85 nmol/l respectively). Oestradiol levels also increased significantly (p = 0.006) from the early follicular to the preovulatory phase (45.85 +/- 5.34 vs. 79.07 +/- 7.45 pg/ml respectively), Pearson's correlation revealed a statistically insignificant correlation between kisspeptin and oestradiol in all three phases. Conclusion: Endogenous kisspeptin secretion seems to vary across the different phases of the menstrual cycle and is not related to serum oestradiol.