Explain the role of hormones in controlling the menstrual cycle and pregnancy, limited to FSH, LH, progesterone and oestrogen

SouravNovember 15, 2024

Answer

The menstrual cycle and pregnancy are regulated by a complex interplay of hormones, primarily follicle-stimulating hormone (FSH), luteinizing hormone (LH), progesterone, and oestrogen. Each of these hormones plays a specific role in controlling the physiological changes that occur during these processes.

Role of Hormones in the Menstrual Cycle

1. Follicle-Stimulating Hormone (FSH):
   • Production: FSH is produced by the anterior pituitary gland.
   • Function:
     • FSH stimulates the growth and maturation of ovarian follicles at the beginning of the menstrual cycle. Each follicle contains an immature egg (oocyte).
     • As the follicles develop, they produce oestrogen, which plays a crucial role in preparing the uterine lining for potential implantation.
2. Luteinizing Hormone (LH):
   • Production: LH is also secreted by the anterior pituitary gland.
   • Function:
     • A surge in LH levels triggers ovulation, which is the release of a mature egg from the dominant follicle around day 14 of the cycle.
     • After ovulation, LH supports the formation of the corpus luteum from the ruptured follicle, which is essential for progesterone production.
3. Oestrogen:
   • Production: Oestrogen is primarily produced by the developing follicles in the ovaries and later by the corpus luteum.
   • Function:
     • Oestrogen promotes the thickening of the endometrial lining in preparation for a fertilized egg. It also regulates FSH and LH levels through feedback mechanisms.
     • Rising oestrogen levels lead to an increase in LH secretion, culminating in ovulation.
4. Progesterone:
   • Production: Progesterone is produced by the corpus luteum after ovulation.
   • Function:
     • Progesterone further prepares the endometrium for implantation by making it more vascularized and nutrient-rich.
     • It inhibits further ovulation during the luteal phase by suppressing FSH and LH secretion. If pregnancy does not occur, progesterone levels drop, leading to menstruation.

Role of Hormones in Pregnancy

1. Oestrogen:
   • During pregnancy, oestrogen levels rise significantly due to production by both the corpus luteum (early pregnancy) and later by the placenta.
   • Oestrogen helps maintain uterine lining integrity, supports fetal development, and stimulates breast tissue growth for lactation.
2. Progesterone:
   • Initially produced by the corpus luteum, progesterone is later produced by the placenta as pregnancy progresses.
   • It plays a crucial role in maintaining pregnancy by preventing uterine contractions, supporting endometrial health, and inhibiting further ovulation during gestation.
3. FSH and LH:
   • During pregnancy, FSH and LH levels remain low due to high levels of oestrogen and progesterone from the placenta. This suppression prevents new follicular development and ovulation during pregnancy.