Reproductive Hormones & the HPG axis Flashcards
Which two reproductive hormones have similar structures?
Testosterone & estradiol
How does the liver inactivate steroids?
Saturation of all double bonds (e.g. progesterone) or by attacking a sulphate or glucuronide (e.g. testosterone)
What are the placental hormones?
PGF2α, progesterone, oestrogen, eCG, hCG
By what methods can hormones exert their effects?
Autocrine – affects the cell producing them
Paracrine – diffuse short distance to affect cells nearby
Endocrine – acts on target cells distant from the site of synthesis
What are the main differences between lipid and water soluble hormones?
Lipid soluble – transported in blood by carrier proteins, diffuse through plasma membrane e.g. estradiol, testosterone
Water soluble – easily travel in blood, bind to receptors on the surface of the cell e.g. GnRH, FSH, LH
What hormones are secreted by the follicle and the corpus luteum?
Follicle – follicular phase – estradiol
Corpus Luteum – luteal phase - progesterone
In which lobe of the pituitary gland is the portal system present?
Anterior lobe
What is the function of the surge centre in the female?
Provides a surge of GnRH, once per oestrus cycle (pre ovulatory surge stimulated by a threshold of oestrogen in the face of low progesterone)
What hormones are produced by the follicle?
Estradiol which feeds back positively on the surge centre, and inhibin which negatively feeds back on FSH
What is luteolysis?
Degeneration of the corpus luteum, causes a drop in progesterone
What are metoestrus and dioestrus?
Metoestrus – early luteal phase
Dioestrus – sustained period of high progesterone
What are the effects of progesterone after ovulation?
Inhibitory feedback on the contractile part of the myometrium & negative feedback on the hypothalamus and pituitary gland
What is a key factor in luteolysis?
PGF2α
In animals when is the first day of the cycle?
First day of oestrus
Is there a surge centre in the male?
No
