In this article, we will discuss about the endocrinology of menstrual and uterine cycle in humans. Several hormones effect these cycles, such as progesterone, estrogen, etc. We will discuss how the levels of these hormones effect the menstrual and uterine cycle. Imbalance in the hormones causes malfunctioning of these cycles which leads to several health problems. Additionally, malnutrition and other environmental factors cause the problems in menstrual and uterine cycle.
The menstrual cycle is a complex physiological process that occurs in women of reproductive age. It involves the interplay of various hormones, which regulate the growth and shedding of the uterine lining. Understanding the endocrinology of the menstrual and uterine cycle is crucial for comprehending the intricate mechanisms behind female reproductive health. This article aims to explore the hormonal changes that occur during these cycles, shedding light on the fascinating interplay between the endocrine system and the female reproductive system. https://academic.oup.com/edrv/article/27/1/17/2355161
ENDOCRINOLOGY OF MENSTRUAL CYCLE:
The menstrual cycle is divided into three phases: the follicular phase, ovulation, and the luteal phase. Each phase is regulated by different hormones, primarily estrogen, progesterone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH).
1. FOLLICULAR PHASE:
The follicular phase begins on the first day of menstruation and lasts until ovulation. During this phase, FSH stimulates the growth and maturation of ovarian follicles, which contain the eggs. As the follicles develop, they produce estrogen, which thickens the uterine lining (endometrium) in preparation for potential implantation.
Ovulation occurs around the 14th day of a typical 28-day menstrual cycle. The surge in LH triggers the release of a mature egg from the dominant follicle. This process is facilitated by the positive feedback of estrogen on the hypothalamus and pituitary gland.
3. LUTEAL PHASE:
After ovulation, the ruptured follicle transforms into the corpus luteum, which secretes progesterone. Progesterone prepares the endometrium for potential implantation by thickening the blood vessels and glands. If fertilization does not occur, the corpus luteum degenerates, leading to a decline in progesterone levels, and the menstrual phase begins.
ENDOCRINOLOGY OF UTERINE CYCLE:
The uterine cycle, also known as the endometrial cycle, is closely linked to the menstrual cycle. It involves the cyclic changes in the endometrium, which prepares the uterus for implantation and supports early pregnancy.
1. MENSTRUAL PHASE:
During menstruation, the shedding of the endometrium occurs due to the withdrawal of estrogen and progesterone. This process is triggered by the constriction of blood vessels, leading to tissue breakdown and subsequent menstrual bleeding.
2. PROLIFERATIVE PHASE:
Following menstruation, the proliferative phase begins. Rising estrogen levels stimulate the growth and repair of the endometrium, increasing its thickness and vascularity. The endometrium becomes receptive to implantation during this phase.
3. SECRETORY PHASE:
During the secretory phase, progesterone dominates, leading to the secretion of glycogen-rich substances by the endometrial glands. This phase prepares the endometrium for embryo implantation and supports early pregnancy.
The endocrinology of the menstrual and uterine cycle is a complex and tightly regulated process involving the interplay of various hormones. Estrogen, progesterone, FSH, and LH play crucial roles in regulating the growth and shedding of the uterine lining. Understanding these hormonal changes is essential for comprehending female reproductive health and diagnosing and treating menstrual disorders. Further research in this field will continue to enhance our understanding of the intricate mechanisms behind the endocrinology of the menstrual and uterine cycle.
Fraser IS, Critchley HO, Broder M, Munro MG. The FIGO recommendations on terminologies and definitions for normal and abnormal uterine bleeding. Semin Reprod Med. 2011;29(5):383-390. doi:10.1055/s-0031-1287652.
Nelson LR, Bulun SE. Estrogen production and action. J Am Acad Dermatol. 2001;45(3 Suppl):S116-S124. doi:10.1067. https://pubmed.ncbi.nlm.nih.gov/11511861
Baird DT. The endocrinology of the menstrual cycle. Methods Mol Biol. 2014;1154:145-169. doi:10.1007/978-1-4939-0659-8_9
Critchley HO, Maybin JA, Armstrong GM, Williams AR. Physiology of the endometrium and regulation of menstruation. Physiol Rev. 2020;100(3):1149-1179. doi:10.1152/physrev.00011.2019