Male Reproductive Physiology Flashcards
At what point in a females life does she secrete more LH than FSH?
During her adult reproductive period
What is one of the earliest events of puberty?
Nocturnal pulses of LH during REM sleep
What is a natural inhibitor of GnRH release and where is it released from?
Melatonin; Pineal gland
When are melatonin levels highest?
During childhood and decline in adulthood
What are the 3 androgens secreted by the testes?
- testosterone
- dihydrotestosterone
- androstenedione
What are fetal Leydig cells responsible for?
Masculinization get the male urogenital tract and inducing testis descent
When do Fetal Leydig cells atrophy?
Shortly after birth
When do adult Leydig cells become fully steroidogenic?
At puberty
What do Leydig cells acquire cholesterol from?
Low-density lipoprotein receptors (LDL) and to a lesser extent high-density lipoprotein (HDL) receptors
What do Leydig cells store cholesterol as?
Cholesterol esters
What is free cholesterol generated by within the testis?
Cholesterol hormone sensitive lipase (HSL)
-it converts cholesterol esters to free cholesterol
Cholesterol is transferred within the mitochondrial membrane via what?
Steroidogenic acute regulatory protein (StAR)
What is cholesterol converted to in Leydig cells?
Pregnenolone
What are the 2 enzymes that other tissues use in converting cholesterol to mineralocorticoids and glucocorticoids that the testis lack?
21 and 11 beta hydroxylase
What is the enzyme that the testes have that converts androstenedione to testosterone?
17 beta-hydroxysteroid dehydrogenase
In the lumen of the seminiferous tubules, testosterone is concentrated by binding to what?
Androgen binding protein (ABP)
What is the main protein that binds testosterone in the blood?
Sex hormone Binding globulin (SHBG)
During what periods in a females life does she secrete for FSH than LH?
Childhood and after her adult reproductive period
What hormone promotes Pregnenolone synthesis?
LH
In what 2 ways does LH promote Pregnenolone synthesis?
- increases affinity of P450SCC (desmolase) for cholesterol
- Long-term action in which it stimulates synthesis of P450SCC
What can be used to treat benign prostatic hypertrophy and male pattern baldness?
5alpha-reductase inhibitors
What androgen stimulates secretion of the sebaceous gland?
DHT
What pathway is the LH receptor on Leydig cells coupled with?
CAMP-PKA pathway
What are Sertoli cells stimulated by?
Testosterone and FSH
What is estradiol important for in Sertoli cells?
Spermatogenesis
What kind of inhibin do males have?
Inhibin B
What does inhibin do?
Negative feedback to anterior pituitary so inhibit secretion of FSH but NOT to the hypothalamus
Where does decapacitation of sperm occur?
In the epididymis
What does decapacitation of sperm mean?
Adding molecules to the membranes of sperm to prevent the acrosomal reaction before contact with the egg
What does the seminal vesicles add to ejaculatory fluid that reacts with cervical fluid to make it less thick and also causes backward peristalsis in the uterus and Fallopian tube to move ejaculatory sperm towards the uterus?
Prostaglandins
Name the disorder: Genetic disorder in which hypothalamic neurons responsible for releasing GnRH fail to migrate into the hypothalamus. Delayed or absent puberty. IMPAIRED SENSE OF SMELL.
Kallman’s syndrome
Name the disorder: extra X chromosome. Appear normal at birth. At puberty, increased levels of gonadotropins fail to produce normal testicular growth & Spermatogenesis. Androgen production is usually low but gonadotropin levels are high so it is primary hypogonadism. Seminiferous tubules largely destroyed leading to infertility.
Klinefelter syndrome
