Hormonal Axis Physiology

Question 1

What hormones does the anterior pituitary release?

Answer 1

Thyroid Stimulating Hormone (TSH)
Adrenocorticotropic Hormone (ACTH)
Follicle Stimulating Hormone (FSH) and Luteinising Hormone (LH)
Growth Hormone (GH)
Prolactin

Question 2

What hormones does the posterior pituitary release?

Answer 2

Oxytocin

ADH

Question 3

What stimulates the anterior pituitary to secrete TSH?

Answer 3

TRH - Thyrotropin-releasing hormone

Question 4

What mechanism regulates thyroid hormone levels?

Answer 4

T3 and T4 sensed by both the hypothalamus and anterior pituitary

This suppresses release of TRH and TSH

Negative feedback

Question 5

which hormones regulate cortisol release

Answer 5

CRH - corticotrophin release hormone (hypothalamus)

ACTH - adrenocorticotrophic hormone (ant. pit.)

Question 6

What diurnal variation is seen in cortisol release?

Answer 6

Typically cortisol levels peak early in the morning

Lowest levels late at night

Question 7

Mechanism that regulates cortisol secretion

Answer 7

Negative feedback

Cortisol sensed by hypothalamus and anterior pituitary -
- suppresses release of CRH and ACTH

Question 8

Actions of cortisol within body:

Answer 8

Inhibits the immune system

Inhibits bone formation

Raises blood glucose

Increases metabolism

Increases alertness

Question 9

where is growth hormone released from?

Answer 9

anterior pituitary

Question 10

What stimulates GH release?

Answer 10

GHRH - growth hormone-releasing hormone
- From the hypothalamus

Also Ghrelin released from stomach

Question 11

What action does growth hormone have?

Answer 11

1. Stimulates IGF-1 release from liver (insulin-like growth factor)

All over the body:

• Stimulates muscle growth
• Increases bone density and strength
• Stimulates cell regeneration and reproduction
• Stimulates growth of internal organs

Question 12

What hormone supresses GH release from ant. pit.

Answer 12

Somatostatin

Question 13

What stimuli cause the release of PTH:

Answer 13

• Low serum calcium
• Low magnesium
• High serum phosphate

Question 14

What action does PTH have on bone:

Answer 14

increases activity and number of osteoclasts

- causing resorption of calcium from bone into blood -> ↑ serum calcium

Question 15

What action does PTH have on kidneys

Answer 15

Increase in calcium reabsorption - ↓ calcium excreted in urine

Stimulates kidneys to:
- converts vitamin D3 into calcitriol (active form of vit D)

• Calcitriol - promotes calcium absorption in small intestine

Question 16

what supresses release of PTH?

Answer 16

High serum calcium

Negative feedback

Question 17

actions of aldosterone in nephron:

Answer 17

Increases sodium reabsorption - distal tubule

Increase potassium secretion - distal tubule

Increase hydrogen secretion - collecting ducts

Question 18

What stimulates release of aldosterone from adrenals?

Answer 18

Agiotensin II

Question 19

where is renin released from?/ and in response to what

Answer 19

Juxtaglomerular cells - sit in afferent arterioles of the kidneys

Renin secreted in response to low BP

Question 20

Action of renin?

Answer 20

Converts angiotensinogen producted in liver to angiotensin I

which is then converted to angiotensin II by ACE