Aldosterone and Cortisol

Question 1

Aldosterone – Production/Release

Answer 1

Question 2

Aldosterone - Action

Answer 2

• The principal site of aldosterone action is on the distal and collecting tubules of the kidney
• Promotes Na+ retention and enhances K+ elimination
• Secondarily induces osmotic retention of H₂O, expanding the ECF volume and therefore blood pressure.

Question 3

Describe Mineralocorticoid Receptor Activation

Answer 3

Question 4

Draw the HPA Axis

Answer 4

Question 5

Anterior Pituitary Cells and Hormones: Corticotroph

Answer 5

Pituitary population: 15-20%

Product: ACTH b-lipotropin

Target: Adrenal gland Adipocytes Melanocytes

Question 6

Anterior Pituitary Cells and Hormones: Thyrotroph

Answer 6

Pituitary population: 3-5%

Product: TSH

Target: Thyroid gland

Question 7

Anterior Pituitary Cells and Hormones: Gonadotroph

Answer 7

Pituitary population: 10-15%

Product: LH, FSH

Target: Gonads

Question 8

Anterior Pituitary Cells and Hormones: Somatotroph

Answer 8

Pituitary population: 40-50%

Product: GH

Target: All tissues, liver

Question 9

Anterior Pituitary Cells and Hormones: Lactotroph

Answer 9

Pituitary population: 10-15%

Product: PRL

Target: Breasts, gonads

Question 10

What is CRH?

Answer 10

• Polypeptide hormone secreted by parvocellular neuroendocrine cells from paraventricular nucleus of hypothalamus
• 41 amino acids
• Also produced in some peripheral cells (T cells, placenta)

Question 11

What is ACTH?

Answer 11

• Polypeptide hormone secreted from anterior pituitary
• 39 amino acids
• Circadian pattern of release

–Highest levels of cortisol are in early AM following ACTH release

–Depends on sleep-wake cycle, jet-lag can result in alteration of pattern

•Opposes the circadian pattern of growth hormone secretion

Question 12

Describe the regulation of ACTH secretion

Answer 12

–CRH and ADH

–Stress

–Hypoglycemia

Question 13

How does the HPA axis regulates cortisol secretion?

Answer 13

1. ACTH from the anterior pituitary corticotropes stimulates the

adrenal cortex (zona fasciculata and zona reticularis) to secrete cortisol.

2. ACTH stimulates both the growth secretory output of these two cortical layers
3. Alongside this diurnal rhythm and stress mediate release

Question 14

What are the metabolic effects of cortisol?

Answer 14

1. ↑ the [blood glucose] via gluconeogenesis at the expense of protein and fat stores
2. Inhibits glucose uptake and use by many tissues, increasing blood glucose.
3. Stimulates protein degradation in many tissues, increases the blood amino acid concentration (drives gluconeogenesis).
4. Facilitates lipolysis

Question 15

What are the permissive actions of cortisol?

Answer 15

Cortisol permits catecholamines to induce vasoconstriction

Question 18

Cortisols role in Adaptation to Stress

Answer 18

Cortisol plays a key role in adaptation to stress. Possibly because faced with a life-threatening situation increased availability of blood glucose would help protect the brain

Question 19

Describe the anti-Inflammatory and Immunosuppressive Effects of cortisol

Answer 19

Cortisol exerts anti-inflammatory and immunosuppressive effects. Cortisol interferes with almost every step of inflammation (eg suppressing neutrophil migration) and has profound effects on the immune system (egr inhibiting antibody production by lymphocytes)

Question 20

Glucocorticoid Receptor Activation

Answer 20

• S: steroid
• CBG: corticosteroid-binding globulin
• HSP: heat shock protein
• GRE: glucocorticoid response element