H-P-G Axis Physiology

Question 1

Which hormones do the hypothalamus secrete?

Answer 1

Gonodotrophin releasing hormone (GnRH)
Growth Hormone releasing factor (GRF)
Somatostatin (SS)

Question 2

Which hormones do the pituitary secrete?

Answer 2

Growth hormone (GH)
Leutinising hormone (LH)
Folllicle-stimulating hormone (FSH)

Question 3

Name some of the hormones the ovaries secrete?

Answer 3

Androstenedione => Oestrogen

Sex steroids

Myriad growth factors

Question 4

What hormone secreted in the hypothalamus stimulates production of GH in the pituitary?

Answer 4

GRF

Question 5

What hormone secreted in the hypothalamus stimulates production of LH and FSH in the pituitary?

Answer 5

GnRH

Question 6

What hormone secreted in the pituitary stimulates production of production of Insulin-like growth factor-1 (IGF-1) in the liver?

Answer 6

Growth hormone

Question 7

What are the functions of IGF-1?

Answer 7

Inhibits further GRF and GH secretion

Mediates most effects of GH

Stimulated production of GnRH

Question 8

What effect does LH have on the ovaries?

Answer 8

Stimulates proliferation of follicular cells and theca cells

Question 9

What do theca cells produce in the ovaries and what is the further effect?

Answer 9

Produce androstenedione which acts on granulosa cells which then produces oestrogen

Question 10

What effect does FSH have on the ovaries?

Answer 10

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

Question 11

What is the combined effect of LH and FSH together on the ovaries?

Answer 11

Stimulate:

• production of oestrogen and progesterone
• ovulation

Question 12

What effect does LH have on the testes?

Answer 12

Acts on Leydig cells to stimualte production of testosterone

Question 13

What effect does FSH have on the testes?

Answer 13

Acts on Sertoli cells to stimulate proteins such as:

• androgen-binding protein
• inhibin B

Question 14

What is the combined effect of LH and FSH together on the testes?

Answer 14

Exert negative feedback on hypothalamus and pituitary

Stimulate secondary sexual characteristics

Question 15

How does testosterone and inhibin B affect production of the gonadotrophins (LH and FSH)?

Answer 15

Inhibit further production of LH and FSH