The study measured two hormones, irisin and kisspeptin, in women at different points of their menstrual cycle and found they rise and fall together in a pattern, with the highest levels in the luteal phase and the lowest during menstruation.

The menstrual cycle is a complex biological process regulated by the hypothalamic-pituitary-ovarian axis, resulting in cyclical hormonal changes that affect various physiological systems. Irisin, a myokine linked to energy metabolism, and kisspeptin, a key regulator of gonadotropin-releasing hormone (GnRH) secretion, are emerging as essential modulators of reproductive function. This study evaluated phase-specific changes in serum irisin and kisspeptin levels and their associations with food intake during the menstrual cycle in healthy premenopausal women. A total of 21 women with regular menstrual cycles were included. Fasting blood samples were collected during the follicular, luteal, and menstrual phases. Serum irisin and kisspeptin-1 levels were measured using ELISA. Our results demonstrated significant phase-dependent fluctuations in both hormones (p < 0.05). Notably, irisin and kisspeptin levels were lowest during the menstrual phase and peaked in the luteal phase. Moreover, a moderate positive correlation between irisin and kisspeptin was observed in the follicular phase (r = 0.453, p < 0.05), whereas moderate negative correlations were found during the luteal and menstrual phases. These findings highlight the dynamic interplay between energy metabolism and reproductive hormones during the menstrual cycle. The observed associations suggest that irisin and kisspeptin may jointly contribute to the hormonal regulation of female reproductive physiology. This study provides novel insights that may enhance our understanding of the endocrine mechanisms underlying menstrual cycle regulation and female reproductive health.