Lesson 3 - The Female Hormone Cycle

Objectives:

  • Identify what hormones help control the changes that occur during your cycle.
  • Learn where in the body female hormones are produced.
  • Understand the hormone-driven events that occur during your menstrual cycle.

Major Points:

  • Your menstrual cycle is driven by hormones.
  • Female hormones are produced in several areas of the body, including the brain, pituitary gland, adrenal glands, and ovaries. 
  • The female cycle begins with the release of GnRH (gonadotropin-releasing hormone).
  • Different hormones produce different symptoms that can help you determine where you are in your cycle.
  • Estrogen drops significantly after ovulation.
  • Your BBT (basal body temperature) rises as a result of the hormone progesterone.

You know that your cycle is driven by hormones but did you know that different hormones play different roles from week to week? Your monthly hormone cycle begins on the first day of your period and resets on the first day of your next period. Throughout your cycle, an array of hormones like estrogen and progesterone surge through the body affecting everything from your energy levels to your libido. These hormones are carried throughout the body via your bloodstream. The female hormones that control your cycle and fertility are produced in the following areas of the body:

•    Hypothalamus: A section of the brain responsible for the production of many essential hormones.
•    Anterior pituitary gland: Also in the brain, this gland secretes six hormones: growth hormone (GH), prolactin (PRL), luteinizing hormone (LH), follicle-stimulating hormone (FSH), thyroid-stimulating hormone (TSH), and adrenocorticotropic hormone (ACTH).
•    Ovaries: Produces hormones like estrogen which trigger menstruation.
•    Adrenal glands: Located on the top of each kidney, the adrenal glands perform a number of bodily functions including the production of hormones cortisol and aldosterone.

The menstrual cycle is a complex process that involves many different glands and hormones. These hormones are secreted during the four phases of the menstrual cycle: menstruation, the follicle phase, ovulation, and the luteal phase. These female hormones are what make conception possible.

1. During the first phase of your cycle, menstruation, the hypothalamus produces the GnRH hormone. Every 60 to 90 minutes, GnRH is sent through the bloodstream from the hypothalamus to the pituitary gland. This process lasts from the beginning of menstruation until ovulation. During the menstruation phase, the GnRH signals the secretion of FSH from the anterior pituitary gland. In the days before ovulation, the LH is secreted which triggers ovulation.

2. The FHS hormone stimulates the follicles in the ovaries to develop and mature. Once a cycle, one of these follicles containing the ovum will become dominant. The ovum is later released during ovulation. These developing follicles are responsible for the production of estrogen.

3. The estrogen that is released by the dominant follicle and the other developing follicles cause the endometrium (lining of the uterus) to thicken and grow. This process is crucial for the fertilized ovum to properly implant in the event of pregnancy.

4. Around day 7 of your cycle, the dominant follicle takes control. All eggs within the non-dominant follicles fail to maintain nourishment and die along with the follicular cells.

5. The dominant follicle causes a significant rise in estrogen. This rapid increase in estrogen production can cause noticeable symptoms such as an increase in cervical fluid. One to two days prior to ovulation, estrogen is at its peak.

6. The surge of estrogen in the body causes the release of LH. This LH surge is essential for ovulation and occurs about 12 to 24 hours before ovulation. The hormone then travels through the bloodstream to the ovary. Once in the ovary, enzymes create a hole in the dominant follicle’s sac, causing the follicle to rupture and release the ovum. The ovum then enters the fallopian tube where it stays for 24 hours as it waits to be fertilized. Estrogen drops significantly after ovulation.

7.  After ovulation, the dominant follicle becomes the corpus luteum which governs hormone production during the luteal phase. During this phase, the corpus luteum continues to secrete small amounts of estrogen, as well as progesterone. Like estrogen, progesterone helps develop the endometrium. As progesterone is produced, you may see your BBT rise.

8. If an egg is fertilized and implanted during ovulation, the life of the corpus luteum is extended and continues to produce estrogen and progesterone to maintain the endometrium. In addition, the pregnancy hormone hCG is produced about 7 to 10 days after ovulation as the fertilized egg implants. Further into the pregnancy, the placenta takes over hormone production.

9. If the egg fails to be fertilized, no pregnancy occurs and the corpus luteum dies. This results in progesterone levels falling and the start of a new cycle.