Module 2.4 Hormonal Control in Males Flashcards
Leydig cells convert ______ to _______
Leydig cells convert cholesterol to testosterone
Describe the synthesis of Testosterone
Cholesterol is converted to pregnenolone via cholesterol side-chain cleavage enzyme
Pregnenolone is converted to progesterone via 3-beta-hydroxysteroid dehydrogenase
Progesterone is converted to androstenedione via 17-hydroxyprogesterone
Androstenedione is converted to Testosterone via 17-beta-hydroxysteroid dehydrogenase
Testosterone is secreted by the ________ and can be converted to Dihydrotestosterone (DHT) via the enzyme _______
Testosterone is secreted by the testes and can be converted to Dihydrotestosterone (DHT) via the enzyme 5-alpha-reductase
Where in the testosterone synthesis chain is Estrone and Estradiol synthesized?
- Estrone:
- After Progesterone is converted to Androstenedione, Androstenedione is converted to Estrone via aromatase
- Estradiol
- After Androstenedione is converted to Testosterone, Testosterone is converted to Estradiol via aromatase
What is the pulsatile release of GnRH?
GnRH is secreted from the hypothalamus every 90min
Where does GnRH act and via which portal vessels?
GnRH acts on the Anterior Pituitary via hypothalamohypophyseal portal vessels
GnRH triggers __________
GnRH triggers pulsatile LH and FSH release
- slow removal from the plasma
FSH acts on _________ to elicit _______
FSH acts on sertoli cells to elicit spermatogenesis
LH acts on ______ to elicit _______
LH acts on Leydig cells to elicit Testosterone secretion
- Testosterone diffuses to seminiferous vesicles
- Enters sertoli cells to facilitate spermatogenesis
Fill in the flow chart
In which tissues is testosterone converted to estradiol and by means of which enzyme?
In the brain, liver, adrenal, muscle and adipose tissue
via enzyme aromatase
What happens to testosterone in the prostate?
In the prostate, testosterone is converted to dihydrotestosterone (DHT) via 5-alpha-reductase
DHT is more potent and is responsible for secondary sex characteristics
What are three components that could contribute to male infertility
Low sperm count
Sperm transport
Evironmental factors
What is the leading cause of male infertility?
Low sperm count (oligospermia)
Absence of sperm (azoospermia)
Oligospermia can be related to central nervous system dysfunction in what way?
Oligospermia (low sperm count) can be related to lower than normal function of hypothalamus and/or pituitary gland
What are four treatment options for oligospermia?
Low sperm count
Tx:
- GnRH stimulatory agonists
- Gonadotropins
- Anti-estrogen drugs
- estrogen decreases GnRH and LH/FSH in males
- Prolactin antagonists
- Pituitary tumour - prolactin decreases GnRH
Oligospermia may be related to dysfunction in the testes, how?
- Testes may not respond to gonadotropins (FSH/LH)
- Structural abnormalities – surgical correction (eg restore bloodflow)
- Permanent damage
- no production of viable sperm
- Chemotherapy or radiation — irreversible damage
What is a varicocele?
Impacts?
Varicose vein in the scrotum
- Impacts:
- As this testicular vein grows it increases pressure in the scrotum
- Also increases heat (reduces temperature control) which decreases spermatogenesis
What is cryptorchidism? How might it lead to oligospermia?
a condition in which one or both of the testes fail to descend from the abdomen into the scrotum.
- testosterone production is intact but spermatogenesis requires a cooler temperature than physiological temp
What is Orchitis?
Testicular inflammation
- temporary or permanent infertility
- Infection
—- STIs, bacterial/viral (eg mumps)
In which case would a treatment with adrenal hormones help to restore fertility?
In the case of autoantibodies to sperm
- treatment with adrenal hormones (cortisol) suppresses immune overactivity
What types of sperm transport complications could interfere with fertility?
- Improper development/function of secondary accessory ducts
- Vas deferens
- Occlusion by testicular vein
- Scar tissue
- Both require surgical correction
- Vas deferens
- Malfunction or inactivity of secondary accessory gland
- underdevelopment
- Androgen treatment
- Prostate infection “prostititis”
- Sterility
- underdevelopment
What are five environmental factors that might contribute to temporary or permanent infertility?
- Smoking
- decreases motility
- increased number of structurally abnormal sperm
- Lower T levels
- Pollution
- Heavy metals
- industrial chemicals
- endocrine disruptors (eg xenoestrogens/phytoestrogens)
- Chronic drug use:
- Alcohol, marijuana (both decrease GnRH = decrease HPG cascade)
- Anabolic steroids
- Age
- Heat
How can the abuse of anabolic steroids (synthetic androgens) be a cause of infertility?
- Overstimulate prostate = prostate cancer
- Aggression
- Decreased GnRH, LH, FSH
- decrease in endogenous testosterone and spermatogenesis in sertoli cells
- synthetic androgens DO NOT gain access to seminiferous tubules
- Decreased testicular size, low sperm count
- Addictiveness
- decrease in endogenous testosterone and spermatogenesis in sertoli cells
