HR Lesson 9: Mineralocorticoids

What is the primary mineralocorticoid produced in the adrenal cortex?

Aldosterone

What type of hormone is aldosterone?

Steroid hormone that circulates either bound (mostly) or free in the blood

What does aldosterone participate in regulating?

Homeostasis of essential ions (Na+, K+, H+)

Water homeostasis (water follows sodium)

Blood volume and blood pressure

pH

What is the correct sequence of events from renin release to aldosterone secretion?

Angiotensinogen —> Angiotensin I —> Angiotensin II —> Aldosterone

What are the stimuli of the renin-angiotensin-aldosterone system?

1. Hypotension

2. Hyperkalemia

3. Hyponatremia

4. Increase sympathetic activation

What is the only stimuli that stimulates aldosterone release directly to the adrenal cortex without stimulating renin?

Hyperkalemia

What part of the kidney stimulates the secretion of renin from stimuli?

Juxtaglomerular apparatus

What does renin do?

Converts angiotensinogen to angiotensin I

What does Angiotensin converting enzyme do?

Convert Angiotensin 1 to Angiotensin II

What are the target tissues of aldosterone?

Epithelial cells in the distal tubules and collecting ducts (nephrons)

Also epithelial cells in the salivary glands, sweat glands, gastric mucosa, and the large intestine

Where does aldosterone bind to target receptors?

Aldosterone is lipophilic so it binds to mineralocorticoid receptors in the cytoplasm

How does aldosterone influence the Na+/K+ pump?

Increases sodium pumping into the blood and enhances potassium and hydrogen ion pumps into the lumen

What does aldosterone stimulate?

Reabsorption of Na+ and water

K+ excretion

H+ excretion

What are the primary mechanisms of action of aldosterone in the kidneys?

Stimulation of sodium reabsorption and excretion of potassium

What is hypoadrenocorticism?

Deficient production of aldosterone and cortisol

What does hypoadrenocorticism lead to?

Glucocorticoid deficiency first, followed by mineralocorticoid deficiency

What happens if there is a cortisol deficiency?

Poor stress response, weakness, inability to maintain blood glucose levels due to impaired gluconeogensis, resulting in hypoglycemia and lethargy

What happens if there is an aldosterone deficiency?

Sodium and water loss —> dehydration and hypovolemia

Potassium and hydrogen ion retention —> hyperkalemia and metabolic acidosis

Affects pacemaker cells —> bradycardia

What is the most common drug used in treatment of hypoadrenocorticism?

Hormonal supplementation therapy

What is the therapeutic goal of hypoadrenocorticism treatment?

Glucocorticoid and mineralocorticoid replacement

Control of hypoglycemia

Fluid therapy

Supportive nutritional care

What happens due to excessive production of aldosterone?

Continuous retention of sodium and water —> hypervolemia and systemic arterial hypertension

Uncontrolled loss of potassium and hydrogen ions —> hypokalemia and metabolic alkalosis W

What is the effect of hypokalemia from hyperaldosteronism?

Slows action potential transmission in nerves and muscles, reduced neuromuscular excitability cause muscle weakness, hyporeflexia, and lethargy

What is the most common drug used in tx of hyperaldosteronism?

Spironolactone - receptor antagonist

What is the therapeutic goal of spironolactone?

Control hypertension and hypokalemia

What is the therapeutic target and mechanism of action of spironolactone?

Block aldosterone mineralocorticoid receptors in the distal tubule and collecting duct of the nephrons