HPG Axis & Hormones

Question 1

What is the function of GnRH in the HPG axis?

Answer 1

GnRH stimulates the anterior pituitary to release LH and FSH, which regulate reproductive functions.

Question 2

How does negative feedback regulate the HPG axis?

Answer 2

Hormones like testosterone, estrogen, and inhibin suppress GnRH, LH, and FSH production when their levels are high.

Question 3

What are tropic hormones and give examples?

Answer 3

Tropic hormones regulate other endocrine glands. Examples include LH, FSH, and ACTH.

Question 4

How do negative and positive feedback mechanisms differ?

Answer 4

Negative feedback reduces the effect of a stimulus, maintaining homeostasis, while positive feedback amplifies a response, such as during ovulation.

Question 5

How do water-soluble hormones function?

Answer 5

They bind to membrane receptors, activating intracellular signalling pathways like cAMP to alter cell activity.

Question 6

How do lipid-soluble hormones function?

Answer 6

They diffuse through cell membranes, bind to intracellular receptors, and influence gene transcription.

Question 7

What are the primary differences between water-soluble and lipid-soluble hormones in terms of transport and action?

Answer 7

Water-soluble hormones travel freely in the bloodstream and act on membrane receptors, while lipid-soluble hormones require carrier proteins and act on intracellular receptors.

Question 8

How does progesterone prepare the uterus for implantation?

Answer 8

It thickens the endometrium, reduces myometrial motility, and induces the production of thick cervical mucus.

Question 9

What is the function of inhibin in the reproductive system?

Answer 9

Inhibin suppresses FSH secretion from the anterior pituitary to regulate gametogenesis.

Question 10

What are the steps in the male HPG axis?

Answer 10

1.Hypothalamus secretes GnRH
2. Promotes release of LH and FSH
3. LH stimulates Leydig cells in testis to produce testosterone
4. FSH stimulates Sertoli cells to produce androgen binding globulin and inhibin.
5. Increased levels of testosterone and inhibin have a negative feedback effect on the pituitary and hypothalamus
6. Results in decreased production of LH and FSH.

Question 11

What are the steps in female HPG axis?

Answer 11

1. Hypothalamus secretes GnRH
2. Promotes release of LH and FSH
3. LH and FSH bind to the varies and stimulate production of oestrogen and inibin
4. Increasing levels of oestrogen and inhibin cause negative feedback effect
5. Leads to the decreased production of GnRH, LH and FSH

Question 12

What are examples of water soluble hormones?

Answer 12

Insulin, LH, FSH, HCG and amines derived from single amino acids e.g., epinephrine

Question 13

What are examples of lipid hormones?

Answer 13

Steroid hormones e.g., testosterone, estradiol and cortisol

Question 14

What are the mechanism of action of water soluble hormones?

Answer 14

1. Bind to membrane receptors
2. Activates G protein
3. This activates adenylyl cyclase
4. This catalyses the conversion of ATP to cAMP
5. cAMP activates protein kinases
6. This phosphorylates proteins in the cytoplasm allowing them to alter cell activity

Question 15

What are the mechanism of action of lipid soluble hormones?

Answer 15

1. Diffuse through plasma membrane
2. Binds with receptor in cytoplasm, forming receptor-hormone complex
3. Complex enters the nucleus and triggers gene transcription
   4.Transcribed mRNA is translated into proteins that alter cell activity