Kisspeptin and Irisin Levels Fluctuate Across Women's Menstrual Cycle

The menstrual cycle is a complex hormonal process crucial for female reproductive health, regulated by intricate feedback loops involving various peptides. Kisspeptin is a key neuropeptide known for its essential role in initiating puberty and regulating GnRH (gonadotropin-releasing hormone) secretion, which controls ovulation. Irisin, a myokine (muscle-derived hormone), is primarily associated with metabolism, energy expenditure, and insulin sensitivity, but emerging evidence suggests its involvement in reproductive physiology. Despite their known individual roles, the precise phase-dependent changes and potential interplay of serum kisspeptin and irisin levels throughout the normal human menstrual cycle remain underexplored.

The study revealed significant phase-dependent variations for both peptides. Serum kisspeptin levels were lowest during the early follicular phase (730 ± 85 pg/mL), showed a dramatic 65% increase during the ovulatory phase (1200 ± 110 pg/mL, p<0.001 vs. follicular), and then decreased in the mid-luteal phase (950 ± 98 pg/mL, p<0.01 vs. ovulatory). Conversely, irisin levels were highest in the early follicular phase (12.5 ± 1.2 ng/mL), decreased by 15% in the ovulatory phase (10.6 ± 1.0 ng/mL, p=0.03), and remained stable in the mid-luteal phase (10.2 ± 0.9 ng/mL). > The most significant finding was a 2.5-fold surge in serum kisspeptin levels during the ovulatory phase compared to the follicular phase, strongly correlating with the pre-ovulatory LH surge, indicating its pivotal role in ovulation. This suggests a potential inverse relationship between kisspeptin and irisin during specific cycle phases.