HPG axis Flashcards
How do peptide hormones work?
Peptide hormone works at cell surface resulting in secondary messenger system activation.
How do steroid hormones work?
Steroid hormones pass through plasma membrane (lipid bilayer) into cytosol or nucleus where they bind receptors. Receptor complex bound to hormone moves into nucleus where hormone works on DNA.
What are the properties of lipid soluble hormones?
Hydrophobic
— So need to be transported in blood by carrier
proteins
— Diffuse through plasma membrane
— Alters expression of genes at level of nucleus
e.g., steroid hormones: oestradiol (type of oestrogen),
testosterone (sort of androgen)
What are the properties of water soluble hormones?
Hydrophillic
— Easily travel in blood
— Bind to receptors on the surface of the cell
— Results in series of intracellular events
e.g., GnRH, FSH, LH, IGF (insulin like growth factor)
What hormone comes from the hypothalamus?
— GnRH (Gonadotrophin releasing hormone) To control release of other hormones
What hormones are produced from the pituitary?
— Gonadotrophins = FSH &LH pituitary gonadotrophins (follicle stimulating hormone & luteinising hormone). Prolactin: Ant Pit
— Oxytocin: released from Post Pit
What hormones are produced from the gonads?
Ovary: oestrogens, progesterone, inhibin, oxytocin, relaxin + some testosterone
Testis: testosterone + other androgens, inhibin (inhibits
FSH), oestrogen
What hormones are produced from the placenta?
Prostaglandin F2a (important in regulation ovulation and ovarian cycle), progesterone, oestrogen, eCG & hCG (equine & human chorionic gonadotrophin made by chorion)
What are steroids formed from?
Dietary cholesterol. Contain 4 rings (3 6 rings and 1 5)
What converts testosterone to estradiol?
Aromatase
What transports neurohormones from the hypothalamus to the anterior pituitary?
The portal system.
The male hypothalamus releases constant pulses of what? And what effect do these pulses have?
GnRH.
GnRH acts to stimulate LH release which stimulates pulses of testosterone release.
What is the function of leydig cells?
They have LH receptors and positive stimulation results in testosterone production.
What is the function of sertoli cells?
The have FSH receptors and on positive stimulation secrete inhibin which negatively feeds back onto the anterior pit and FSH secretion.
Which two hypothalamic neurons produce GnRH in females?
Surge and tonic centre neurons.
males have not surge centre
