How menstruation changes in cycles

　　How does menstruation cycle? female One of the physiological characteristics of the reproductive system is its cyclical changes, and menstruation is an important symbol of this cyclical change. The menstrual cycle is mainly regulated by the interaction between the hypothalamus-pituitary-ovary. The hypothalamus regulates the function of the pituitary gland, and the pituitary gland regulates the function of the ovary.

　　Uterus The endometrium undergoes cyclic changes under the action of ovarian hormones. The sex hormones produced by the ovaries, in turn, act on the hypothalamus and pituitary gland, affecting the release of gonadotropin-releasing hormone, follicle-stimulating hormone, and luteinizing hormone, which is the so-called feedback effect ； When it is inhibited from release, it is called negative feedback, and when it is promoted, it is called positive feedback.

　　The relationship between changes in blood hormones during the normal menstrual cycle and the ovaries and endometrium is as follows: After the corpus luteum atrophy in the previous menstrual cycle, the secretion of estrogen and progesterone decreases, releasing the inhibition of the hypothalamus and pituitary gland. Gonadotropin-releasing hormone produced by the hypothalamus enters the anterior pituitary gland through the pituitary portal system, promoting the secretion and release of follicle-stimulating hormone and luteinizing hormone. Under the synergistic effect of follicle-stimulating hormone and luteinizing hormone, the follicles in the ovary gradually mature and produce estrogen, causing proliferative changes in the endometrium. After the follicles mature, the first peak of estrogen appears in the body.

　　The increase in estrogen secretion has a feedback effect on the hypothalamus and pituitary gland, inhibiting the production of follicle-stimulating hormone, promoting the increase in luteinizing hormone secretion, and causing a luteinizing hormone peak, triggering ovulation. After ovulation, the corpus luteum is formed and secretes estrogen and progesterone. Under their joint action, the endometrium undergoes typical secretory phase changes. After ovulation, estrogen levels temporarily decrease, followed by a second, lower peak.

　　The large amounts of estrogen and progesterone secreted by the corpus luteum inhibit the hypothalamus and pituitary gland through negative feedback, causing the secretion of follicle-stimulating hormone and luteinizing hormone to decrease, and the corpus luteum begins to shrink. After the corpus luteum atrophies, the secretion of estrogen and progesterone decreases, and the endometrium cannot be supported by sex hormones, causing necrosis, shedding, and menstruation. After the corpus luteum atrophies, the inhibition on the hypothalamus and pituitary gland is also released, allowing gonadotropin-releasing hormone to be secreted again, and another menstrual cycle begins.