Pregnancy Hormones and Menstrual Cycle

Ovarian Cycle

FOL (follicular, ovulation, and luteal)

FSH

Secreted by the anterior pituitary gland. Matures the ovarian follicle. Highest and most important during follicular phase.

Ovulation (Day 14)

A surge of LH causes the mature follicle to rupture and expel a mature egg. Occurs on day 14 of a 28 day cycle. First LH and estrogen peak 10-36 hours before ovulation, then estrogen drops during ovulation. Fallopian tubes become active by creating currents to help carry the egg to the uterus. An egg lives about 24 hours unless it's joined with a sperm. Cervix produces thin, clear, stretchy, slippery mucous. This environment will catch, nourish, and help sperm travel to the egg. Symptoms: spotting, increase in discharge, increased libido, slight temp increase, lower and cramping. Ovulation take place 14 days before menstruation regardless of cycle length. Pain during release of egg is called mittelshmerz.

Secretory Phase (Days 15-28)

After ovulation, the corpus luteum releases progesterone to thicken the endometrium in preparation for implantation. Occurs at the *same time as the luteal phase*. Absence of fertilization by day 23 causes ovarian hormones to decrease and the corpus luteum to degenerate. Estrogen and progesterone decrease and the endometrium undergoes involution (menstruation occurs).

Proliferative Phase (Days 5-14)

Corresponds to follicular phase of the ovarian cycle. Begins with increase of estrogen causing endometrial glands to enlarge in preparation for implantation of fertilized egg. Cervical mucous becomes thin, clear, stretchy, and more alkaline for enhance opportunity for fertilization with sperm. Begins day 5 of menstrual cycle and lasts until time of ovulation. Occurs *at the same time as the follicular phase*.

Menstrual Phase (Days 1-4)

Ischemia causes the spiral arteries to rupture, causing blood to release into the uterus and causing the endometrial lining to slough. The corpus luteum degenerate, estrogen and progesterone fall, and the endometrial wall sloughs away and passes through vagina. Beginning of the menstrual flow marks the end of on menstrual cycle and the start of a new one. Lasts 3-7 days, 1 oz of blood in volume/cycle

Endometrial (Uterine) Cycle

MPOSI (Menstruation, Proliferative, Ovulation, Secretory, Ischemic)

Prostaglandins

Not technically hormones. Produced by tissues, not glands. Increase during follicular maturation. Releases ovum inside the graafin follicle during ovulation. Large amount found in menstrual blood. Prostaglandin F2a causes menstrual cramps/pain. Elevated levels are found in dysmenorrhea. Tx: NSAIDs

Ischemic Phase (Days 24-28)

This phase only occurs if fertilization has not occurred. Corpus luteum degenerates causing estrogen and progesterone levels to drop sharply. Arterioles in the endometrium spasm, causing ischemia of the basal layer. Ischemia causes shedding of the endometrium down to the basal layer. Menstruation occurs

Luteal Phase (Days 15-28)

Begins at ovulation and lasts until menstrual phase of next cycle. Occurs during days 15-28. After follicle has ruptured and released egg, it closes and forms a corpus luteum. Corpus luteum secretes progesterone. Progesterone prepares the endometrium for implantation and causes the temp to rise 0.5-1 degree. Progesterone induces the endometrial glands to secrete glycogen, mucus... If egg not fertilized, corpus luteum degenerates, estrogen and progesterone decrease, and the endometrium undergoes involution: causing menstruation 14 days after ovulation. FSH and LH lowest during this phase.

LH

Secreted by the anterior pituitary. Matures follicles and closes the ruptured follicle, forming the corpus luteum. Estrogen falls a day before ovulation (day 13) and progesterone levels rise.

Progesterone

Secreted by the corpus luteum. Increase just before ovulation and peak 5-7 days after ovulation. Swells and increases secretion of the endometrium during luteal phase. Reduces uterine contractions. Calming effect-allows pregnancy to be safely maintained.

Estrogen

Secreted by the ovaries. Develops and matures the follicle. Highest at the end of the proliferative phase, right before ovulation. After ovulation, estrogen drops sharply and progesterone dominates. Induces sloughing of endometrial lining. Increases the size & weight of the uterus due to increased glycogen, amino acids, electrolytes, blood supply and water.

GnTH

Secreted from the hypothalamus throughout cycle. Pulsates slowly during follicular phase and increases during luteal phase. Induces release of FSH and LH to assist w/ ovulation.

Follicular Phase (Days 1-14)

The hypothalamus initiates the process in which follicles in the ovary grow to form a mature egg whose purpose is for fertilization. Day 1 of the menstrual cycle and continues until ovulation, 10-14 days later. Estrogen increases and causes rapid growth of the endometrium and myometrium to allow for a thick lining that is easy for the ovum to stick to in event of pregnancy. The hypothalamus prompts the pituitary gland to release FSH. FSH stimulates the ovary to produce 5-20 immature follicles. Each follicle houses an immature oocyte or egg. One follicle will fully mature and rupture/expel a mature egg. This is ovulation. FSH and LH highest during this phase.