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Female Hormones: Synthesis and Function
Reproductive System Hormone
Though endocrine, paracrine signaling also important hereCross-talk Between different cells within each gonad and Between endocrine and germ cells that are close to each other Between cells of maternal and fetal originAutocrine function also important
In addition, peptides that are synthesized in the hypothalamus and that initiate functioning of the hypothalamic-pituitary-gonadal axis may also be produced locally within the gonads and placenta, where they may have additional functions
Steroid Hormones
Synthesized from cholesterol
Steroid Hormones
17-ketosteroids
17-hydroxycorticoids or 17-hydroxycorticosteroids
OH
20,22-desmolase
17-hydroxylase
Gonadal Hormones Synthesis
3β-ol-dehydrogenase and Δ4,5-isomerase
17,20-desmolase
aromatase
Gonadal Hormones Synthesis
3β-ol-dehydrogenase and Δ4,5-isomerase
aromatase
aromatase
17β-OH-steroid dehydrogenase
3β-ol-dehydrogenase and Δ4,5-isomerase
Gonadal Hormones Synthesis
17β-OH-steroid dehydrogenase
5α-reductase
3α-reductase
3β-ol-dehydrogenase and Δ4,5-isomerase
aromatase
Gonadal Hormones Synthesis
Ovary
ovary orchestrates the development and release of a mature oocyte and also elaborates hormones (e.g., estrogen, progesterone, inhibin) that are critical for pubertal development and preparation of the uterus for conception, implantation, and the early stages of pregnancy
Estrogen production in the ovary
Feed back pathway
Harmonal level during menstrual cycle
Levels of FSH & LH Hormones
Effects on the Female Genitalia
Effects on Endocrine Organs
Effects on the Central Nervous System
Effects on the Breasts
Female Secondary Sex Characteristics
significant plasma cholesterol-lowering action
Function of estrogen
Progesterone
Principal target organs of progesterone are the uterus, the breasts, and the brain
Cyclic changes in the cervix and vagina
Maintenance of Pregnancy
Function of Progesterone
progesterone receptor is bound to a heat shock protein in the absence of the steroid, and progesterone binding releases the heat shock protein, exposing the DNA-binding domain of the receptor. The synthetic steroid mifepristone (RU 486) binds to the receptor but does not release the heat shock protein, and it blocks the binding of progesterone.
Substances that mimic the action of progesterone are sometimes called progestational agents, gestagens, or progestins. They are used along with synthetic estrogens as oral contraceptive agents
Mechanism of Action of Progesterone
Polycystic Ovary SyndromeEssentials of DiagnosisClinical or biochemical evidence of hyperandrogenism. Oligoovulation or anovulation. Polycystic ovaries on ultrasonography.
Polycystic ovary syndrome (PCOS) is a common endocrine disorder affecting 4–7% of women of reproductive age and is a common source of chronic anovulation. The underlying etiology is unknown, although most of these women have an aberration of gonadotropin stimulation. This is manifested by an increased release of luteinizing hormone (LH) relative to follicle-stimulating hormone (FSH), resulting in an increased production of androstenedione and testosterone by ovarian theca cells
Polycystic Ovary Syndrome
Females…
Females…The female reproductive
system is much more complicated than the male reproductive system.
The male produces sperm at a
constant rate, whereas the female goes through a complicated cycle in which an egg matures and is released over the course of a month.
The hormonal levels of the female fluctuate throughout her reproductive years until menopause.
The creation of an ovum is called oogenesis: Ovaries contain follicles. Follicles are made up of the primary oocyte and the granulosa cells. The primary oocyte undergoes meiosis and becomes a mature ovum. The granulosa cells provide nutrients for the oocyte.
Although the ovary contains around 400 000 follicles, only about
400 or so will develop into mature ovum (from age 12 to about age 50).
Since many genetic disorders occur to the offspring of older mothers, it is theorized that as the follicles mature, they become genetically inferior.
Menopause signals the end of the female reproductive life as all
ovarian hormones, the female sex hormones, cease to be secreted.
As the primary oocyte goes through meiosis I, one of the cells garners the majority of the cytoplasm and grows to a much larger size... this is the secondary oocyte. The remaining portion is termed a polar body. The secondary oocyte pushes against the ovary wall and eventually bursts through... ovulation.
Surrounding follicle cells around the burst form the corpus luteum
which secretes hormones essential for pregnancy. If pregnancy does not happen, the corpus luteum degenerates after about 10 days.
The secondary oocyte undergoes meiosis II in the oviduct. The one
garnering all the cytoplasm this time is the mature ovum. The other is another polar body.
As with the male, there is a negative feedback loop that regulates
the production of female sex hormones (progesterone and estrogen).
The Feedback LoopHypothalamus releases
gonadotropic releasing hormone (GnRH) to the pituitary
Pituitary releases FSH to stimulate the follicles in the ovary to mature
The follicle releases estrogen which causes the endometrial lining of the uterus to thicken
This estrogen, at midcycle, also causes the pituitary to release LH and stop secreting FSH.
The Feedback LoopThe rise in LH secretions cause
ovulation to occur .
LH makes the remaining follicles turn into the corpus luteum.
The corpus luteum secretes both progesterone and a small level of estrogen which promote the building up of the endometrium.
As progesterone and estrogen build up in the female, they inhibit the release of FSH and LH from the pituitary.
This causes the corpus luteum to deteriorate and thus decrease the levels of estrogen and progesterone which causes menstruation.
Menstrual Cycle
The whole thing lasts about 28 days, but can be irregular due to a number of factors.
There are 4 phases to the menstrual cycle.
Flow Phase: Days 1-5: This is the shedding of the endometrial lining and is the only phase of the female cycle that can be determined externally. It takes about 5 days for the entire lining to be shed.
Follicular Phase: Days 6-13: The follicles are developing inside the ovary and as they mature they are releasing estrogen.
Menstrual CycleOvulation: Day 14: The egg bursts from the
ovary and is caught by the fimbriae and sent into the oviduct. The corpus luteum is made from the follicles around where the egg burst. Slight dip in estrogen level when the burst occurs.
Luteal Phase: Days 15-28:Estrogen and progesterone are secreted by the corpus luteum. Progesterone continues to stimulate the thickening of the uterine lining as well as preventing further ovulation and uterine contractions. If the egg is not fertilized, the concentrations of estrogen and progesterone drop which causes a return to the flow phase.
Birth control pills contain high concentrations
of progesterone which inhibits ovulation and thereby prevents conception.
Thank you