Male repro Flashcards
Gonadal sex determinant in males
-SRY gene encodes testis determining factor (leads to production of androgens)
XX male
- SRY gene translocates to the X chromosome during meiosis
- Will develop into male but normal testes never produced
Androgens produced by the Leydig cells promote:
- Differentiation of Wolffian duct
- Prostate development
Anti Mullerian hormone
- From sertoli cells
- Causes mullerian ducts to degenerate
What hormone does wolffian duct development require?
Testosterone
What hormone does prostate development require
DHT
What stimulates formation of male external genitalia?
- DHT
- Begins at about 10 weeks gestation
How does GnRH work?
-Binds G protein coupled gonadotroph receptors and activates PLC which ultimately causes Ca release, DAG production, and protein kinase C activation
Effects of a constant supply of GnRH
- Downregulation of GnRH receptors
- Decreased secretion of LH and FSH
Leydig cells
- Sensitive to hCG and LH
- Produces testosterone
Sertoli cells
- Respond to FSH
- Produce aromatase, growth factors, and inhibin
Negative feedback routes
- Testosterone can inhibit GnRH release from hypothalamus and LH release from anterior pituitary
- Inhibin can work on anterior pituitary to inhibit FSH release
Kallmann syndrome
- Hypogonadotropic hypogonadism
- Lack LH and FSH due to lack of GnRH neurons
- Also have congenital anosmia
5-alpha reductase
-Converts testosterone to DHT
Desmolase
- Converts cholesterol to pregnenolone
- Rate limiting step
- Upregulated by LH
Male pseudohermaphroditism
- 5alphareductase deficiency: DHT levels reduced, prostate won’t develop correctly and neither with external genitalia
- Androgen insensitivity syndrome: androgen receptors defective
Androgenic effects of angrogens
- Maturation of sex organs
- Development of secondary sex characteristics
Anabolic effects of androgens
- Promote protein synthesis and growth of tissues
- Muscle growth
- Increase in bone density
What causes a higher hematocrit in men?
-Androgens increase the expression of erythropoeitin from kidneys
What regulates male sex behavior
-Estrogens
Kennedy’s Disease (Spinobulbar muscular atrophy)
- Mutation in androgen receptors
- Lower motor neuron disease
- Expansion of CAG repeat
- Toxic gain of function
- X linked
Senesence (andropause)
- No abrupt loss of fertility
- Testosterone decreases
- Quantity and quality of sperm also decreases
- FSH and LH increase
Finasteride (propecia)
-Blocks production of DHT, used to treat male pattern baldness
Spermatogenesis
- Initiated at puberty by FSH via sertoli cells
- Further supported by LH driven increases in testosterone and sertoli cell growth factors
