Androgens Flashcards
What cells synthesize testosterone? What is the precursor to this?
Cells of Leydig
Cholesterol
What are the two general functions of androgens?
Androgenic effects
Metabolic effects
What are the androgenic effects of androgens?
Maturation and continued function of male reproduction
What are the metabolic effects of androgens?
Regulates formation of Muscle, bone, marrow, liver
Describe the HPA axis in regards to the gonadotropes.
GnRH from hypothalamus goes to the pituitary gonadotropes, which release LH and FSH into the blood. These go to the testicular Leydig cells or Sertoli cells.
What are the cells in the pituitary that are stimulated by GnRH? What do they release?
Pituitary gonadotropes
LH and FSH
What is the function of LH in the male? Where does this go?
Stimulates the cells of leydig to secrete Testosterone
What is the function of FSH in the male? Where does this go?
Goes to sertoli cells, to secrete ABP and inhibin
What allows for a higher concentration of LH/FSH in the testicles?
Androgen binding protein
What is the enzyme that is present in the testicles that is not present in the adrenal cortex, and allows for the conversion of androstenedione to testosterone?
17-beta-HSD
What is the function of 5-alpha-reductase?
Converts testosterone into 5-alpha-dihydrotestosterone, a more potent form of testosterone
What is the general way in which GnRH is released from the hypothalamus?
Pulsatile fashion
How does LH increase the production of testosterone?
increasing the expression of cholesterol desmolase
What is the feedback mechanism for LH?
Testosterone inhibits hypothalamus from releasing GnRH
What are the two products of further metabolizing testosterone? What do these do in the HPA axis?
DHT
Estradiol
Inhibit pituitary gonadotropes
Draw out the pathway of cholesterol synthesis.
Draw.
What is the enzyme Leydig cells express that convert androstenedione to testosterone?
17beta-HSD
True or false: testosterone is highly bound to albumin in the blood. What (other) protein is it bound to?
True
Sex hormone binding globulin.
What happens to the amount of sex hormone binding globulin as we age? What is the significance of this?
Decreases, meaning less testosterone circulating as we age.
What is the MOA of testosterone? DHT?
Binds to cytoplasmic receptor, which can then transverse the nucleus, and increase transcription
DHT is the same, but more potent
What is the enzyme that converts testosterone into estradiol?
p450s
What enzyme is found in high concentrations in the prostate? What is the significance of this?
5-alpha-reductase
Increases DHT there
What is the chemical that can freely diffuse into cells, and can then by converted into testosterone? What is the enzyme that does this?
DHEAS
17-beta-HSD
What is the effect of testosterone in the liver in regards to lipids? What is the significance of this?
Increase VLDL and LDL
Decrease
This may be why males have an increased rate of artherosclerosis
What is the effect of testosterone on lipid accumulation in adipocytes?
Inhibits
What is the effect of testosterone on blood glucose levels? How?
Lowers by increasing the expression of glucose transporters on the plasma membrane of adipocytes
What is the effect of testosterone on RBCs?
Increases production of erythropoietin
Why is it that very close monitoring is required when using testosterone replacement therapy in growing children?
May prematurely close the growth plates
What is the gynecological disorder where testosterone is used?
Severe endometriosis
What are the primary causes of hypogonadism? (2)
- Testicular dysfunction (cryptorchidism)
- Klinefelter