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50 Cards in this Set
- Front
- Back
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When is testosterone highest in young men?
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In the morning
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What is the axis that is involved with the production of testosterone?
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HPT axis: hypothalamus, pituitary, testis
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Where does LH act at the testis?
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Leydig cells
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What do leydig cells produce? What stimulates them?
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Testosterone
LH |
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Where does FSH act in the testis?
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Sertoli cells
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What is the function of the sertoli cells?
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Spermatogenesis regulation
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What's the function of FSH?
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Regulate spermatogenesis
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How is it that testosterone is transported from the testes to the circulation?
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Through diffusion
There's not a special pump. |
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How is testosterone carried in the blood?
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Sex hormone binding globulin: 60%
Albumin: 38% Free: 2% |
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What form of testosterone is free for use in the body?
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Testosterone bound to albumin
Free testosterone in the blood |
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What is the effect of testosterone (and its metabolites) on the:
kidney? bone marrow? bone? skin? liver? |
Kidney: stimulation of erythropoietin
Marrow: stimulation of stem cells Bone: accelerated linear growth; closure of epiphyses Skin: hair growth, balding, sebum Liver: synthesis of serum proteins |
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What is the action of testosterone in the male sexual organs?
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Penile growth
Spermatogenesis Prostate growth, function |
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What are the metabolites of testosterone?
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DHT: dihydrotestosterone
Estradiol |
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Specifically, what are the effects of DHT?
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Facial, body hair growth
Acne Scalp hair loss Prostate growth |
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Specifically, what are the effects of testosterone?
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Muscle mass
Skeletal growth Spermatogeneiss Sexual function |
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What are the funcitons of estradiol?
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Bone formation
Breast tissue |
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What's the largest cause of increased estradiol in men?
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Overweight: they have too much fat tissue, where the aromatase is present
They can have estradiol then go back and inhibit the secretion of GnRH, which inhibits testosterone production! |
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What enzyme is responsible for the production of DHT?
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5 alpha reductase
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What's the definition of hypogonadism?
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Reduction in testosterone production
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What is the defect that takes place in primary hypogonadism?
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Testicular failure
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What is the defect that takes place in secondary hypogonadism?
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Hypothalamic or pituitary dysfunction
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What are causes of hypogonadism?
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Primary testicular failure
Obesity HIV Meds Normal aging Cancer Trauma Syndromes (kallman's, pituitary adenoma) |
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What is the cause of hypogonadism in the aging man?
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Natural gradual decrease in testosterone production
Increase in SHBG production (less bioavailable testosterone) Declining leydig cell counts |
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What are signs and symptoms of low testosterone in an adult male?
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Loss of libido; ED
Mood changes Fatigue Osteoporosis Loss of muscle mass, strength Regression of secondary sexual characteristics Oligospermia, azoospermia |
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What are some strongly positive indicators that a person is androgen deficient?
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Lack of sex drive
Less strong erections |
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What are some labs that you can run to diagnose androgen insufficiency?
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Serum total testosterone
These last two should only be measured when you suspect an increase in SHBG Serum free testosterone Serum bioavailable testosterone |
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When should you sample serum total testosterone?
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In the morning, when there's the peak in the circadian rhythm
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What are some conditions that can cause an increase in SHBG?
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Aging
Cirrhosis Hyperestrogenemia Obesity |
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If there is low testosterone, what other labs will you order?
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LH and FSH: primary or secondary?
Serum prolactin: pituitary tumor? |
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Why does a prolactin secreting tumor cause deficiencies in sex hormones?
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You alter the pulsatility of GnRH secretion
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What enzyme responds to androgens in the penis to cause erections?
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NOS
You need this to relax the blood vessels |
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What's the impact of hypogonadism on bone integrity?
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If you don't have sex steroids, bones aren't dense.
You end up getting tons-o-fractures. |
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What's the effect of testosterone on bone density? What mediates this effect?
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Increases bone density
Estradiol is what mediates this. |
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What are the ways that we can deliver testosterone to patients?
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Oral tablets
IM injections Transdermal patches Transdermal gel Buccal mucoadhesive patch |
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What's the hepatic clearance of testosterone?
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SUPER HIGH.
Almost none gets past the liver |
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What is done to testosterone to try and decrease hepatic metabolism/
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Methylation
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What are the side-effects of oral androgens?
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Lowering of HDL cholesterol!
HEPATOTOXICITY! |
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How do you never want to prescribe testosterone?
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Orally.
It's bordering on malpractice |
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How often do you have to give injections of testosterones?
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Once every 2 weeks, ish.
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What are problems with injectibles?
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Supraphysiologic peaks
Subphysiologic troughs |
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What are complications with topicals? Why?
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Skin issues: rashes, blisters, etc.
They put a chemical on the patch that breaks down the stratum corneum that allows the testosterone to get into the blood |
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With patches, what happens to the blood levels of testosterone? Gels?
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Patches: You get a diurnal peak, just like the physiologic release
Gels: you have a constant steady state |
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What are some possible complications of testosterone replacement?
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Polycythemia
Sleep apnea Hepatotoxicity Prostate disease Suppression of spermatogenesis Effects on lipids (LOWERING OF HDL) Edema Gynecomastia |
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Why do you want to be worried about polycythemia secondary to testosterone?
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Too high of a hematocrit is an independent risk factor for heart troubles.
You don't want to stray above 52. |
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What is the effect of testosterone on lipids?
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Lowering of HDL, which then causes dyslipidemia
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What's the problem with giving testosterone to someone prostate cancer?
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You can cause the cancer to grow!
If the PSA grows up faster than .5, then you should have concern. |
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Who should you be cautious about giving testosterone to?
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MARSHALL SHLAFER!
You'll cause his prostate to get even more enlarged, which will most likely cause a complete cessation of urine flow |
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How is it that exogenous testosterone is a good male contraceptive?
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It induces the negative feedback loop, which causes testosterone synthesis in the testis to halt.
What this means is that you're no longer getting a super high testosterone concentration in the testis, which leads to azoospermia |
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What do you need to monitor in patients on testosterone replacement?
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Voiding history, rectal exam, PSA
BP Cholesterol/HDL HCT Liver enzymes |
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In people who have abused steroids, do their HPA axes recover?
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No, sometimes.
You need to replace the hormones. |
