Repro hormones and the HPG axis

Question 1

Describe the generalised signalling pathways of both peptide and steroid hormones

Answer 1

Peptide= bind to surface receptor- stimulates second messengers which trigger cellular response
Steroid hormone= enters cell nucleus which triggers gene transcription which causes the cellular response

Question 2

Which reproductive hormones are produced in the pituitary gland and which lobe are they produced in?

Answer 2

• Gonadotrophins (FSH/LH)= anterior lobe

- Oxytocin= posterior lobe (is technically synthesised in the hypothalamus)

Question 3

List which reproductive hormones are made in the ovary

Answer 3

Oestrogens, progesterone, inhibin, oxytocin, relaxin and some testosterone

Question 4

List that hormones produced in the testes

Answer 4

Testosterone, inhibin, oestrogen

Question 5

Which hormones are produced by the uterus/ placenta?

Answer 5

• Prostaglandin F2 alpha
• Progesterone
• Oestrogen
• eCG

Question 6

List the two ways the liver inactivates steroids and give an example of a steroid which the method applies to.

Answer 6

1= saturates all double bonds (e.g. progesterone)
2= a sulfate or glucuronide is attached which makes it water soluble (e.g. testosterone)

Question 7

What does the hypothalamo-hyophyseal-portal system allow?

Answer 7

• The hormones secreted from the neuroendocrine cells of the hypothalamus to be taken straight to the anterior pituitary .
• Enables regulation of LH and FSH
• Also allows oxytocin to be transported to the posterior pituitary for storage

Question 8

In females where does GnRH production occur?

Answer 8

In two groups of hypothalamic neurons: the surge centre and the tonic centre

Question 9

What effect does progesterone have in the HPO axis?

Answer 9

it exerts negative feedback on the GnRH neurons thus preventing preovulatory follicle development

Question 10

How does luteolysis remove negative feedback in the HPO axis?

Answer 10

In absence of fertilisation the CL undergoes structural & functional regression (luteolysis). Causes a drop in progesterone thus removing negative feedback.