Menstrual Cycle Hormones

Luteinizing Hormone (LH)

LH is secreted by the *anterior pituitary gland* and is REQUIRED for both the *final maturation of preovulatory follicles* and *luteinization of the ruptured follicle*. As a result, *estrogen* production declines and *progesterone secretion continues.* Thus, estrogen levels FALL a day BEFORE ovulation, and progesterone levels begin to RISE.

Progesterone

Progesterone is secreted by the *corpus luteum.* Progesterone levels INCREASE just before ovulation and peak 5 to 7 days after ovulation. During the *luteal phase,* progesterone induces *swelling and increased secretion of the endometrium.* This hormone is often called the *hormone of pregnancy* bc of its *calming effects on the uterus* (reduces uterine contractions), allowing pregnancy to be maintained!!!

Summary of Menstrual Cycle Hormones

1. LH rises and stimulates the follicle to produce estrogen 2. As estrogen is produced by the follicle, estrogen levels rise, inhibiting the output of LH 3. Ovulation occurs after an LH surge damages the estrogen-producing cells, resulting in a decline in estrogen 4. The LH surge results in establishment of the corpus luteum, which produces estrogen and progesterone. 5. Estrogen and progesterone levels rise, suppressing LH output 6. Lack of LH promotes degeneration of the corpus luteum 7. Cessation of the corpus luteum means a decline in estrogen and progesterone output 8. The decline of the ovarian hormones ends their negative effect on the secretion of LH 9. LH is secreted, and the menstrual cycle begins again

Estrogen

Estrogen is secreted by the *ovaries* and is crucial for the *development and maturation of the follicle*. In the endometrial cycle, *estrogen induces proliferation of the endometrial glands*. Estrogen can also cause the *uterus to increase in size and weight* bc of increased glycogen, amino acids, electrolytes, water, and blood supply. Estrogen is predominant at the END of the proliferative phase, directly preceding ovulation. After ovulation, estrogen levels DROP sharply as *progesterone dominates.*

Follicle-Stimulating Hormone (FSH)

FSH is secreted by the *anterior pituitary gland* and is primarily responsible for the *maturation of the ovarian follicle.* FSH secretion is HIGHEST and most important during the first week of the follicular phase.

Gonadotropin-Releasing Hormone (GnRH)

GnRH is secreted from the *hypothalamus* in a pulsatile manner throughout the reproductive cycle. -Pulsates SLOWLY during the follicular phase and INCREASES during the luteal phase -GnRH induces the release of FSH and LH to assist with ovulation

Prostaglandins

Prostaglandins are the primary mediators of the body's inflammatory processes and are essential for the normal physiologic function of the female reproductive system. Prostaglandins are *closely related to a group of oxygenated fatty acids that are produced by the endometrium,* that have a variety of effects throughout the body. Prostaglandins are NOT HORMONES bc they are produced by all tissues rather than by special glands. Prostaglandins *increase during follicular maturation* and play a key role in *ovulation by freeing the ovum inside the graafian follicle.* Large amounts of prostaglandins are found in menstrual blood. This suggests that the pathogenesis of menstrual cramps/pain is due to *prostaglandin F2a*- a potent myometrial stimulant [cramping] and vasoconstrictor, in the secretory endometrium. -Elevated prostaglandin levels are found in the endometrial fluid of women with *dysmenorrhea (painful menses)* and correlates well with their degree of pain. *NSAIDS* have been introduced as the primary choice of treatment of menstrual cramps.

Menstrual Cycle Hormones

The predominant hormones include: -Gonadotropin-releasing hormone (GnRH) -Follicle-stimulating hormone (FSH) -Luteinizing hormone (LH) -Estrogen -Progesterone -Prostaglandins