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24 Cards in this Set
- Front
- Back
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Where are androgens produced?
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Testes mostly
Adrenals also |
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What enzyme converts Testosterone to 17b-Estradiol?
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Aromatase
Estradiol is the most potent estrogen |
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Where is aromatase synthesized?
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The ovary/placenta in females and adipose tissue in males.
After menopause, the only source of aromatase for females is the adipose tissue. |
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Describe the stimulation of testosterone by LH and FSH.
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LH binds a receptor on the Leydig cells that increases testosterone synthesis.
The testosterone travels to the Sertoli cells where FSH has bound a receptor and increased the synthesis of ADP, which binds to testosterone. This maintains the the high levels of testosterone needed for spermatogenesis. |
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Describe LH,FSH stimulation in females.
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LH binds a receptor on the Thecal Cell which increases synthesis of androgens. These androgens travel to the glanulosa cell where FSH has stimulated the synthesis of aromatase. Aromatase converts the androgens to estrogens.
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Describe the pathway of testosterone to DHT.
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Testosterone-SHBG dissociate so testosterone can translocate the cell. Once it does, it is converted to DHT via 5 alpha reductase. DHT then binds the cytosolic androgen receptor, translocates the nucleus and binds the promotor for the transcription of testosterone dependent genes.
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Describe the hormone fluctuation associated with the menstrual cycle.
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The cycle begins with menses when there is low estrogen and inhibin A levels. The low levels allow FSH and LH to be produced in increasing amounts and stimulate the production of a few follicles. As the follicles mature, they secrete increasing amounts of estrogen, which increase the expression of LH and FSH receptors making the follicle more sensitive to these hormones. The increasing estrogen also however inhibits pituitary LH and FSH release.
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Continued.
The decreased gonadotropin levels cause the other follicles to become atretic and one follicle matures. The increased estrogen is now stimulating the uterine endometrium to proliferate rapidly for implantation. The amount of estrogen eventually reaches a point where it induces a positive rather than a negative feedback loop on gonadotroph cells, stimulating LH and FSH release. This LH/FSH surge causes the dominant follicle to swell and eventually rupture. |
Continued.
The ovum is released and makes it way through the fallopian tube where if it becomes fertilized makes its way to the uterus about 4 days later. The remains of the rupture follicle become the corpus luteum and secrete estrogen and progesterone. The presence of progesterone in the second half of the menstrual cycle switches the endometrium from proliferative to a secretory state. The endometrium now begins synthesizing proteins for implantation and the blood supply to the endometrium increases. |
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Continued.
The corpus luteum has a lifespan of about 14 days. If a blastocyst doesn't implant in that time it ceases production of estrogen and progesterone. |
The inhibition of FSH and LH disappears and they are free to be released and stimulate the generation of new follicles.
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What is PCOS?
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PolyCystic Ovarian Syndrome
The causes are unknown, but it results in increased plasma androgens, and masculinization. Also, anovulation and irregular menstruation. |
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What are the 2 possible treatments?
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Estrogen-Progesterone to negatively feedback on androgen synthesis and anti-androgen drugs.
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Describe the hormone fluctuation associated with the menstrual cycle.
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The cycle begins with menses when there is low estrogen and inhibin A levels. The low levels allow FSH and LH to be produced in increasing amounts and stimulate the production of a few follicles. As the follicles mature, they secrete increasing amounts of estrogen, which increase the expression of LH and FSH receptors making the follicle more sensitive to these hormones. The increasing estrogen also however inhibits pituitary LH and FSH release.
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Continued.
The decreased gonadotropin levels cause the other follicles to become atretic and one follicle matures. The increased estrogen is now stimulating the uterine endometrium to proliferate rapidly for implantation. The amount of estrogen eventually reaches a point where it induces a positive rather than a negative feedback loop on gonadotroph cells, stimulating LH and FSH release. This LH/FSH surge causes the dominant follicle to swell and eventually rupture. |
Continued.
The ovum is released and makes it way through the fallopian tube where if it becomes fertilized makes its way to the uterus about 4 days later. The remains of the rupture follicle become the corpus luteum and secrete estrogen and progesterone. The presence of progesterone in the second half of the menstrual cycle switches the endometrium from proliferative to a secretory state. The endometrium now begins synthesizing proteins for implantation and the blood supply to the endometrium increases. |
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Continued.
The corpus luteum has a lifespan of about 14 days. If a blastocyst doesn't implant in that time it ceases production of estrogen and progesterone. |
The inhibition of FSH and LH disappears and they are free to be released and stimulate the generation of new follicles.
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What is PCOS?
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PolyCystic Ovarian Syndrome
The causes are unknown, but it results in increased plasma androgens, and masculinization. Also, anovulation and irregular menstruation. |
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What are the 2 possible treatments?
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Estrogen-Progesterone to negatively feedback on androgen synthesis and anti-androgen drugs.
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What are the 3 theorized etiologies of PCOS?
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LH Hypothesis - Increased LH stimulates thecal cells to produces androgens.
Insulin Hypothesis - Insulin resistance causes increased insulin levels, which decrease SHBG and increases free Testosterone levels Ovarian Hypothesis - An abnormal increase in enzyme production in thecal cells causing greater thecal production of androgens |
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Why do high levels of LH in PCOS prevent ovulation, when the normal menstrual cycle needs an LH surge for ovulation to occur?
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Women with PCOS do not have the necessary 3:1 LH:FSH ratio. In addition, the absence of estrogen prevents the LH surge required for ovulation to occur
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What are the 2 infertility disorders associated with disruption of the hypothalamic-pituitary axis?
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PCOS
Prolactinoma |
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Describe the prolactin's natural contraception
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Prolactin inhibits GnRH and LH/FSH release. This suppresses ovulation during breast feeding
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What are the examples of reproductive tract disorders that involve inappropriate growth of estrogen/testosterone dependent tissues?
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Breast/Prostate cancer
Endometriosis/endometrial hyperplasia |
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How do you treat estrogen dependent breast cancer?
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ER antagonist (fulvestrant)
Selective modulator (tamoxifen) ET synthesis inhibitor (aromatase inhibitors) |
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How do you treat an androgen dependent prostatic hyperplasia or metastatic prostate cancer?
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Androgen enzyme inhibitor
AR antagonist |
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How do you treat endometriosis?
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GnRH agonists (suppress estrogen)
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