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69 Cards in this Set

  • Front
  • Back
When is genetic sex determined?
At conception
What determines the male genotype?
-SRY gene on the Y chromosome
-The presence of testosterone and MIF
What do the presence of testosterone and MIF ensure?
That normal internal AND external genitalia develop.
What does MIF do?
Causes the mullerian ducts (fallopian tubes) to regress.
What are the 2 types of testosterone that control male reproductive development?
-Testosterone (prohormone)
-DHT (more potent form)
What does Testosterone itself regulate?
Male reproductive tract development (wolfians)
What does DHT itself regulate?
Male genitalia development
What is SRY?
The sex-determining gene on the Y chromosome that induces the gonads to differentiate into the testes.
Where does testosterone and MIF come from?
The testes, after the SRY gene tells the gonads to become testes.
So in utero, before the baby is even born, what 3 hormones do you see rise during the first 8 weeks?
-MIF (to inhibit the fallopian tubes)
Why do LH and FSH rise early in utero?
For the same reason that they do in female babies; SOMATIC SEX DIFFERENTIATION.
What does the presence of LH and FSH in the male fetus cause?
Steroidogenesis - the production of androgens
What would this do in females?
Cause virilization
What hormones rise after birth between 3-7 months in the male baby?
Another surge of LH/FSH
Why does this LH/FSH surge occur in male babies?
For the same reason as in females - we don't know, but maybe brain sex differentiation
What are testosterone levels like in childhood?
Low, but measurable.
What is the function of testosterone during childhood?
It's necessary for normal growth and just being normal.
Is putting on body fat the switch for puberty in males like it is in females?
What does trigger the hypothalamic pulses of GnRH to begin in males at puberty?
We don't know
What is the result of the increase in GnRH pulses?
-Increased FSH/LH
-Wakes up Testosterone
How long does the reproductive age extend in males?
It goes on ad infinitum
What is usually the thing that prevents reproduction in males?
Plumbing problems
What are the 2 important androgens?
1. Testosterone
2. DHT - dihydrotestosterone
What is DHT?
A much more potent form of testosterone that is formed by enymatic conversion.
What enzyme makes DHT from testosterone?
5-alpha reductase
Why is 5-alpha reductase important to know?
Because there are specific drugs that act to inhibit it to reduce the effects of androgens.
What are some 5-alpha reductase inhibitors?
-Propecia (hair follicles are very sensitive to testosterone)
-Proscar (prostate cancer that is induced by testosterone)
What are the 2 main sites of androgen production?
What is the primary androgen secretion from the adrenals?
DHEA sulfate
What is the primary androgen secretion from the testes?
Where is most DHT produced?
By PERIPHERAL conversion from testosterone
What other androgens are made in males?
Estradiol and Estrone
Where are the Estradiol and Estrone made?
Mostly from peripheral conversion of precursors.
What enzyme converts testosterone to estrogens?
Where is Aromatase in men?
-Some in testes
-Most in fat
What causes men to be feminized?
How does Testosterone exert its effect on cells?
By binding to a nuclear receptor and inducing protein synthesis
What does a target tissue do if it wants more action for the same amount of testosterone?
Converts it to DHT with 5 alpha reductase
In the male, when puberty begins, what does LH do?
Stimulates the Leydig cell to produce TESTOSTERONE
(LTL - leydig and theca both produce androgen via LH stim)
What does Testosterone stimulate at puberty?
1. Linear growth
2. Spermatogenesis
3. Secondary sex characteristics
What is the primary stimulator of spermatogenesis?
(LTL FGS - FSH stimulates granulosa and sertoli)
What hormones rise in addition to LH/FSH during puberty?
Why does GH increase?
Because the TESTOSTERONE stimulates it!
What do high prolactin levels do during puberty?
Induce hypogonadism
How does Prolactin cause hypogonadism?
By inhibiting the gonadotrophs from releasing LH/FSH, so there is no development and spermatogenesis.
So what do high levels of prolactin cause in
-Females at puberty
-Males at puberty
Females = amenorrhea
Males = hypogonadism
So what is the main change that occurs at puberty?
Pulsatile release of GnRH increases from the hypothalamus
What does the pulsatile GnRH stimulate?
Pulsatile release of FSH and LH from the pituitary
What are the 2 main effects of the LH and FSH?
-LH stimulates the leydig cell to produce testosterone and have virilizing effects
-FSH stimulates the Sertoli cell to support spermatogenesis
What is necessary for the adequete production of sperm?
BOTH the testosterone from the leydig cells, AND the FSH stimulation.
Does all of the testosterone from the leydig cells only cause virilizing effects and stimulate sertoli spermatogenesis?
No, a little bit is converted to estradiol in the sertoli cells via aromatase like in girls.. but only a little bit.
What is the Sertoli cell's other function other than spermatogenesis?
Production of INHIBIN
What is inhibin?
A hormone that inhibits FSH and GnRH release.
So what type of feedback is exerted by FSH and LH?
Does inhibin work as a male contraceptive?
In addition to stimulating spermatogenesis, what does FSH binding its receptor on Sertoli cells stimulate?
The production of ABP
What is ABP?
Androgen binding protein
How does ABP function?
As an ANDROGEN SINK that sucks up testosterone and holds onto it, to increase the local concentration.
What is the effect of an increased local concentration of testosterone?
The sertoli cell and spermatogonia are BATHED in testosterone
What are the 3 visible results of puberty in males?
1. Penile growth
2. Pubic hair
3. Growth spurt
What is the termination of the growth spurt caused by?
The gonadotropins
Why is taking androgens for increasing muscle mass bad?
Because it actually causes feminization.
How does taking androgens cause feminization?
By conversion via aromatase in adipose tissue.
What genetic disease can cause hypopituitarism?
Hereditary hemochromatosus
What does hereditary hemochromatosus do?
Causes iron deposits in the pituitary that suppress the output of especially Gonadotrophs (LH/FSH)
If a man has no testes but has measurable testosterone, where is it coming from?
The adrenals.
What results from hypopituitarism?
Lack of development of the testes.
What is a bad side effect of the increased iron?
It gets taken up by the thyroid and causes primary hypothyroidism.
Does hereditary hemochromatosus affect the adrenals?
No - they put out everything fine.