Reproductive Endocrinology Flashcards
What are hormones found in the ovary?
Oestrogen and progesterone
What happens to the water soluble hormones?
They can float around in the bloodstream but need to enter through G-protein receptors into the cells via ATP and cAMP mechanisms. Once within cells they cause a cascade through protein kinase phosphorylising enzymes of interest. This causes the response in the cell.
How do lipid hormones enter the cell?
They need a transport protein to travel around the blood but can diffuse into the cells directly. They then activate receptor hormones in the nucleus changing the gene expression. This newly formed mRNA creates new proteins
What are the actions of gonadotropins - males?
FSH and LH travels from pituitary to the gonads where they act. FSH acts in the serotoli cells to help support soerm. They LH works on the leydig cells which can secrete testosterone
Actions of the gonadotropins - females?
LH works on the Theca cells to make androstenedione. Astrostenedione works with FSH in the granulosa cell to make estradiol.
FSH works on the granulosa cells to make Estradiol.
What is the actions of testosterone?
Male reproductive function e.g make sperm
Secondary make characterus5uce
Make sex determination and genital development.
What are the actions of oestradiol?
Endometrial proliferation during menstrual cycle
Female genital development
Secondary female sex characteristics
What does progesterone regulates?
Endometrial secretion and vascularisation during menstrual cycle
Maintains pregnancy and support embryo
What do Hormonal contraceptions do?
Manipulation of steroid gonadal hormones
What does hormonal contraceptives do in females?
Suppress ovulation via negative feedback of progesterone
Oestrogen in combined pill provides additional feedback and promotes progesterone receptor expression
Secondary effects on female genital tract
What does hormonal contraceptive in males do?
Suppress spermatogenesis via negative feedback of testosterone
What happens if you stop taking contraception?
Own HPG axis reawakens
Negative feedback in HPG axis?
Gonadotropin releasing hormone from the hypothalamus causes release of LH and FSH from pituitary which act in the ovary. Oestrogen, progesterone and androgens act back in the pituitary and hypothalamus to reduce secretion of LH/FSH/GnRH
What is positive feedback in HPG axis especially in the sertoli and granulosa cells?
Activins are hormones produced by Sertoli cells and granulosa cells which encourage FSH secretion from anterior pituitary
How is positive feedback happening when a follicle grows?
Follicles growing produce more oestrogen which at certain thresholds had a positive affect in FSH secretion and the LH surge
What is the positive feedback when a pregnancy happens?
The blastocyst makes HcG so causes FSH to rise and LH, progesterone to increase.
How does lactation work?
Baby suckles at teat and this sends nerve impulses to the brain causing oxytocin (from posterior pituitary) and prolactin (from anterior pituitary) to be released.
What does prolactin do?
Causes alveoli to swell and secrete milk. There is however a steroid block from placenta preventing lactation before birth. There is a negative feedback on FSH/LH levels
What does oxytocin do?
Causes smooth muscle contraction of the myoepithelial cell around the alveoli making milk eject. This also induces labour
What is the anti-mullarian hormone?
Critical for sex determination in male embryos
What activates AMH?
Sox9 in Sertoli cells which inhibits the development of the Müllerian duct which would normally make fallopian tubes, vagina, uterus etc.
Where is AMH made in females and what does it inhibit/ unaffected by?
Made in granulosa cells and inhibits follicular development. It is unaffected by gonadotropins/steroid hormone
Why is AMH used clinically?
It’s a reliable way to reflect growing follicles