3. Sex steroids Flashcards
What are sex steroids?
Sex steroids = sex hormones - hydrophobic
List sex steroid classes
Do sex steroids only act on gonads?
No, have effects on many tissues - many cell types have receptors for the hormones
What are the mechanisms used by steroids to induce response
What are the main reproductive steroid hormones?
Main reproductive steroid hormones:
- progesterone
- estradiol
- testosterone
- dihydrotestosterone
What is the steroidogenesis mechanism in ovaries?
Granulosa + theca cells: androstenedione in theca cells - transported through blood into granulosa cells -> converted into estradiol
What are the potential targets of contraception in the mensutrual cycle?
What is the combined contraceptive pill?
Combined contraceptive pill:
- combination of estrogen + progesterone analogues
- inhibit FSH and LH release to prevent follicle development, egg maturation, ovulation + other actions (unreceptive endometrium, cervical mucus, egg transport in oviduct)
- side effects: nausea, weight gain, change in libido
- failure rate 2-8%
What is progesterone only contraceptive?
Progesterone only contraceptive:
- endometrium less receptive, cervical mucus, follicle development
- can be used in breast feeding - doesn’t affect
- for older women, smokers, history of thrombosis
- daily pill, depot, implant, intrauterine IUD
Explain emergency contraception
Emergency contraception (plan B)
Explain fetal steroidogenesis in sheep
Sheep steroidogenesis requires cortisol:
Fetus: adrenal cortex + HPA maturation in fetus -> cortisol into placenta
Placenta: cortisol in TE cells stimulates 17alpha-hydroxylase and aromatase expression => fetal steroidogenesis in placenta
Explain fetal steroidogenesis in humans
In late pregnancy when adrenal cortex develops - fetus itself secretes 17alpha hydroxylase (not placenta as in sheep) - transported into placenta (TE cells) where steroidogenesis occurs = in humans cooperation between fetal adrenal gland and placenta
Summary
