The Physiology of the Menstrual Cycle: From Ovarian Follicles toEndometrial Shedding

Abstract

Background:
The menstrual cycle is a fundamental physiological rhythm in women that reflects the finely
coordinated interplay between the hypothalamic–pituitary–ovarian (HPO) axis and the
endometrium. It ensures reproductive capacity while serving as an indicator of systemic health.
Disturbances in this cycle are often linked to conditions such as polycystic ovarian syndrome
(PCOS), endometriosis, and luteal phase defects.
Objective:
This review aims to consolidate current knowledge on the physiology of the menstrual cycle,
focusing on ovarian follicular dynamics, hormonal regulation, endometrial changes, and their
clinical significance.
Discussion:
The cycle is broadly divided into ovarian (follicular, ovulatory, luteal) and uterine (proliferative,
secretory, menstrual) phases, each governed by hormonal rhythms and feedback loops. The
hypothalamus releases gonadotropin-releasing hormone (GnRH), stimulating pituitary secretion
of FSH and LH, which regulate folliculogenesis and ovulation. Post-ovulation, corpus
luteum–derived progesterone transforms the endometrium into a receptive state. In the absence
of fertilization, luteolysis leads to withdrawal of hormonal support, causing endometrial ischemia
and menstrual shedding. Disturbances in these processes can lead to infertility, irregular
bleeding, and systemic endocrine disorders. Beyond reproduction, cyclical fluctuations in
estrogen and progesterone influence immunity, cardiovascular function, metabolism, and
neuropsychological health.

Conclusion:
Understanding menstrual physiology, from ovarian follicle development to endometrial
shedding, is essential for advancing reproductive medicine and women’s health. It has
implications for diagnosing menstrual disorders, developing contraceptives, improving assisted
reproductive technologies, and addressing broader systemic effects of hormonal fluctuations.