Sex Steroids

Question 1

Menstrual cycle phases

Answer 1

▪️proliferative phase- estrogen

▪️secretory phase- progesterone

Question 2

Ovarian cycle

Answer 2

▪️primary follicle 
▪️growing follicle 
▪️mature follicle 
▪️ovulation 
▪️empty follicle 
▪️corpus luteum- produces progesterone 
▪️corpus luteum regresses 
-only regresses if there has been no fertilisation and implantation. The embryo releases hCG which helps maintain corpus luteum so progesterone can maintain thickness of wall.

Question 3

FSH target

Answer 3

▪️males
-stimulates Sertoli cells in testes-support sperm maturation
▪️ females
-growth and maturation of ovarian follicles

Question 4

LH target

Answer 4

▪️males
-binds to receptors on Leydig cells and stimulates synthesis and excretion of testosterone- stimulates spermatogenesis
▪️females
-theca cells secrete testosterone- converted to estrogen by Granulosa cells

Question 5

Male HPG axis feedback

Answer 5

▪️testosterone produced in Leydig cells have a negative feedback effect on the AP and H.
▪️inhibin produced by Sertoli cells have a negative feedback effect on the AP.

Question 6

Female HPG axis feedback

Answer 6

▪️estradiol produced in ovaries by developing follicle had a negative feedback on H.
▪️progesterone down regulates at H.
▪️inhibin down regulates at AP.

Question 7

Proliferative phase

Answer 7

▪️FSH stimulates immature follicle
▪️granulosa and the a cells produce estrogen
▪️LH triggers follicle and egg to speed up growth, enzymes break down follicle walls
▪️surge of LH just before egg is released from follicle

Question 8

Secretory phase

Answer 8

▪️mature egg travels down Fallopian tube
▪️LH triggers follicle to transform and produce progesterone
▪️progesterone down regulates FSH, LH and GnRH in AP and H so other follicles stop growing.
▪️progesterone prepare endometrial longing for implantation

Question 9

Steriodogenic acute regulatory protein(StAR)

Answer 9

▪️rate limiting factor in steroid biosynthesis
▪️moves to mitochondrial outer membrane and makes it possible for cholesterol to move inside the inner membrane of mitochondria
▪️cholesterols then converts into prognenolone- the precursor to sex steroids

Question 10

Steroid transport

Answer 10

▪️very hydrophobic molecules
▪️need to bind with carrier proteins so they can circulate in blood
- sex hormone-binding globulin (high affinity, low biding capacity)
-albumin (low affinity, high biding capacity)

Question 11

Sex hormone clearance

Answer 11

▪️liver
▪️modified to make it water soluble
▪️make them charged so they dissolve in the blood
▪️excreted via kidney

Question 12

Testosterone

Answer 12

▪️primary and secondary sexual characteristics
▪️stimulates sexual desire in men and women
▪️increases bone thickness
▪️increases basal metabolic rate and muscle mass
▪️promotes RBC formation

Question 13

Estrogen

Answer 13

▪️primary and secondly sexual characteristics
▪️decreases bone reabsorption
▪️vasoprotection in men and women