H-P-G Axis Physiology Flashcards
Which hormones do the hypothalamus secrete?
Gonodotrophin releasing hormone (GnRH)
Growth Hormone releasing factor (GRF)
Somatostatin (SS)
Which hormones do the pituitary secrete?
Growth hormone (GH) Leutinising hormone (LH) Folllicle-stimulating hormone (FSH)
Name some of the hormones the ovaries secrete?
Androstenedione => Oestrogen
Sex steroids
Myriad growth factors
What hormone secreted in the hypothalamus stimulates production of GH in the pituitary?
GRF
What hormone secreted in the hypothalamus stimulates production of LH and FSH in the pituitary?
GnRH
What hormone secreted in the pituitary stimulates production of production of Insulin-like growth factor-1 (IGF-1) in the liver?
Growth hormone
What are the functions of IGF-1?
Inhibits further GRF and GH secretion
Mediates most effects of GH
Stimulated production of GnRH
What effect does LH have on the ovaries?
Stimulates proliferation of follicular cells and theca cells
What do theca cells produce in the ovaries and what is the further effect?
Produce androstenedione which acts on granulosa cells which then produces oestrogen
What effect does FSH have on the ovaries?
stimulates proliferation of granulosa cells to produce:
- sex steroids
- myriad growth factors
stimulates increase LH receptor expression on surface of granulosa cells, leads to FSH -ve feedback
What is the combined effect of LH and FSH together on the ovaries?
Stimulate:
- production of oestrogen and progesterone
- ovulation
What effect does LH have on the testes?
Acts on Leydig cells to stimualte production of testosterone
What effect does FSH have on the testes?
Acts on Sertoli cells to stimulate proteins such as:
- androgen-binding protein
- inhibin B
What is the combined effect of LH and FSH together on the testes?
Exert negative feedback on hypothalamus and pituitary
Stimulate secondary sexual characteristics
How does testosterone and inhibin B affect production of the gonadotrophins (LH and FSH)?
Inhibit further production of LH and FSH
