Test 1 Sex Hormones Physiology

Question 1

gonadal hormones and their release

Answer 1

Estrogen and Progesterone

• Hypothalamus – Releases GnRH (gonadotropin releasing hormone)
• GnRH travels to anterior pituitary and produces LH and FSH
• LH and FSH act on ovary causing estrogen and progesterone production
• Negative feedback to the level of hypothalamus and pituitary modulates release of LH and FSH

Question 2

· What produces estrogen?

Answer 2

Female with menstrual cycles (not too young or old)

Ovaries produce estrogen

• In the first part of the menstrual cycle estrogens are produced by the theca and granulosa cells of the ovarian follicle
• After ovulation estrogens (as well as progesterone) are synthesized by the lutenized granulosa and theca cells of the corpus lutem

Note: estradiol is the major estrogen produced by the ovaries AND the rate of estradiol production varies during the menstrual cycle from low early in follicular phase to a preovulatory peak

Question 3

Physiological Roles of Estrogens

Answer 3

• Female growth and altered body fat distribution (creating curves)
• Female sexual maturation: development of vagina, uterus, uterine tubes, breasts, and contribute to pubic and axillary (armpit) hair growth
• Development of endometrial lining in proliferative phase causing the blood build up in the lining (when in coordination with progesterone, estrogens leads to menstrual cycle :periodic bleeding and shedding of lining)
• Estrogens decrease rate of bone resorption
• Cardioprotective: estrogens alter plasma lipid compositions which leads to increased HDL (good cholesterol) and slightly decreased LDL (bad cholesterol) as well as a reduced total cholesterol levels
• aids in women having lower rate of heart disease, but decreases of estrogen in menopause allows heart disease rates to increase
• Blood clotting: estrogens enhance blood coagulability and increase blood clotting after birth

Question 4

What produces progesterone?

Answer 4

• Progesterone is synthesized in the ovaries, testes, and adrenal cortex from circulating cholesterol.
  
  • In the ovary, progesterone is primarily produced by the corpus lutem
• Large amounts of progesterone are also synthesized and released by the placenta during pregnancy
  
  • Plasma progesterone levels peak in the third trimester

Question 5

Physiological roles of progestins (progesterone)

Answer 5

• Endometrial changes in the secretory phase (whichs follows ovulation)
  
  • Creates a more hospitable place for embryo to grow
• Stimulates lipoprotein lipase which favors fat deposition
• Increases basal insulin levels and increases the insulin response to glucose
  
  • In the liver, possibly fascilitated by the effects on insulin, progesterone promotes gylcogen storage (store calories for growing embryo)
• Can increase sodium reabsorption
  
  • Progesterone competes with aldosterone (used to reabsorb sodium) for the mineralocorticoid receptor of the renal tubule which leads to an increased secretion of aldosterone by the adrenal cortex (increased aldosterone=increased Na reaborption=bloating)
• Increases body temperature: possibly by altering temperature regulating centers in hypothalamus
• Increases sensitivity to P_CO2
  
  • Increases a woman’s ventilation response to CO₂ causing more CO₂ to be blown off which decreases arterial and alveolar P_CO2 during pregnancy and luteal phase of menstrual cycle.
• Progesterone and related steriods have depressant and hypnotic effects on the brain

Question 6

Follicular phase

Answer 6

Follicular Phase (day 1-14): Development of follicles in ovary

• FSH begins to increase just before day 1 of the cycle and it stimulates numerous follicles to begin developing
• One follicle will then be selected to become the dominant follicle which produces estradiol (E2) that peaks around day 12.

Question 7

Ovulation

Answer 7

Ovulation (around day 14)

• The estradiol peak around day 12 causes a major increase in LH (LH surge) and a peak of FSH around day 14
• The LH and FSH peaks lead to ovulation-egg release from the follicle

Question 8

Luteal Phase

Answer 8

Luteal Phase (ovulation -day 28)

• Egg travels through fallopian tubes to uterus
• Follicle transitions into corpus lutem which is a fluid filled sac remaining in ovary that begins to release both progesterone and estrogen
  
  • hormones keep the ova (egg) healthy until it can be fertilized
  • Egg only remains viable for about 2 days
• Around day 21, if egg has not been fertilized, the corpus lutem begins to deteriorate causing progesterone and estrogen to peak and then begin a decline

Menses (around day 28)

• When progesterone fall enough, menses occurs