Nuclear Hormone receptors and reproductive anatomy

Question 1

Class 1

Answer 1

• Present in the cytoplasm in the absence of ligand. Ligand binding causes dimerisation and nuclear translocation Agonists: Testosterone Antagonists: Flutamide- treats androgen dependent prostrate cancer Tamoxifen- used to treat oestrogen dependent breast cancer

Question 2

Class 2

Answer 2

• Exist in the nucleus bound to RXR or another heterodimer and corepressors Agonists: levothyroxine; replacement therapy in hypothyroidism

Levothyroxine MOA: acts at thyroid receptors to make up for deficient levels of thyroid hormone

Question 3

Leydig/interstitial cells

Answer 3

Located between the semiferous tubules of the testes and are the main source of androgen hormones in males

• stimualted to produce testosterone in response to the release of lutenizing hormone from the anterior pituitary

Question 4

Testosterone

Answer 4

• main androgen hormone
• primary role is the maturation of genital organs, secondary functions include deepening of voice, growth of body hair, halting linear growth by fusion of the epiphyseal plates in the long bones of the body and behavioural changes such as aggression and mate seeking behaviour.

Question 5

Anterior Pituitary

Answer 5

releases follicle stimulating hormone, which acts irectly on the sertolie cells to stimulate spermatogenisis

Question 6

Secretion of androgen hormones pathway in males

Answer 6

1. Hypothalamus releases gonadotrophic hormone
2. GnRh acts on the anterior pituitary to release FH and LH
3. FSH stimulates gametogenisis in the seminiferous tubules of the sertoli cell and LH acts on interstitial cells resulting in the release of tesosterone.
4. testosterone augments gametogenisis and attenuates the actions of the anterior pituitary

Question 7

Selection of the dominant follicle

Answer 7

• one dominant follicle with increased sensitivity to FSH, others degenerate due to lowering concentrations of FSH
• LH acts on theca cells to stimulate the production of androgens. Androgens then diffuse into the granulosa cells and are converted to oestrogen by aromatase enzymes/
• FSH acts on the granulosa cells to stimulate the production of oestrogen
• Granulosa cells of the dominant follicle are more sensitive to FSH than the others due to increased receptors, allowing this molecule to avoid atresia

Question 8

Hormone levels in the menstrual cycle

and reasons for the changes

Answer 8

Cyclical changes to the secretion of FSH and LH occur due to due to changes in secretion of GrNh from the hypothalamus and also the sensitivity of the pituitray to the hormone

Question 9

Progesterone

Answer 9

Creates a hospitable environment and also prevents uterine contractions which fascilitates the implantion of fertilized eggs