Lesson 9: HR Adrenal glands Mineralocorticoids

What is another name for mineralocorticoids?

Aldosterone

What is the primary mineralocorticoid produced in the adrenal cortex?

Aldosterone

Aldosterone is what type of hormones that circulates wither bound or free in blood?

Steroid hormone

Aldosterone participates in regulating what functions?

Homeostasis of essential ions (Na, K, H)

Water homeostasis

Blood volume and blood pressure

pH

What zone of the adrenal cortex is aldosterone produced in?

Zona glomerulosa

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

Angiotensinogen → Angiotensin 1 → Angiotensin 2 → Aldosterone

What is the system called that produces aldosterone from angeiotensinogen?

Renin Angiotensin Aldosterone System (RAAS)

What are the main stimuli for RAAS?

Hypotension

Hyperkalemia

During Hyperkalemia the increased levels of K+ directly stimulate what?

Adrenal cortex

What are the target tissues for Aldosterone?

Epithelial cells in the distal tubules and collecting ducts of the nephron

If aldosterone is lipophilic where will their receptors be located?

intracellularly

Once aldosterone binds to its receptor what happens within the cells?

Increases the Na/K pumps in the basolateral membrane, Na channels in the apical membrane, creating a Na gradient.

With the increased Na pumps when aldosterone is bound to its receptor, Na starts to flow from the urine back into the body. What does this mean for the water in the urine?

The water will follow the sodium gradient causing water to be retained, this causes BV and BP to be sustained during dehydration or hypovolemia.

Aldosterone also increases the K channels and H pumps in the apical membranes, what does this mean?

Pumps K and H into the urine to be excreted to protect the body from excessive concentrations of these ions. Also it allows better control of the plasma pH in acidosis?

What is another name for Hypoadrenocorticism?

Addisons disease

What is Addisons Disease?

Deficient production of aldosterone and cortisol

In Addisons disease which goes first the cortisol or the aldosterone?

Cortisol

Why is Addisons disease called the great pretender?

Waxing and waning effect, one week animal is doing fine the next they are doing worse.

What are some consequences of a cortisol deficiency?

Poor stress response

Weakness

Inability to maintain blood glucose levels due to impaired gluconeogenesis, resulting in hypoglycemia and lethargy

What are the consequences to an aldosterone deficiency?

Na and water loss leading to dehydration and hypovolemia

K and H ion retention leaning to hyperkalemia and metabolic acidosis

Bradycardia

ECG alterations

What are the most common drugs used in the treatment of Addisons disease?

Hormonal supplementation therapy

What are the therapeutic goals of hormonal supplementation therapy?

Glucocorticoid and mineral0corticoid replacement

Control of hypoglycemia

Fluid therapy

Supportive nutritional care

Addisons crisis is treated as an emergency

What is the therapeutic target of hormonal supplementation therapy?

Supplement missing endogenous hormones

What are the consequences to excessive production of aldosterone?

Retention of Na and water causing hypovolemia and systemic arterial hypertension

Hypokalemia and metabolic alkalosis

Hypokalemia hyperpolarizes excitable cells, slowing action potential transmission in nerves and muscles

Reduces neuromuscular excitability, muscle weakness, hyoreflexia and lethargy

What is the most common drug used to treat hyperaldosteronism?

Spironolactone: Receptor antagonist

What is the therapeutic goal of Spiralactone?

Control hypertension and hypokalemia

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

Block aldosterone mineralocorticoid receptor in the distal tubule and collecting duct of the nephron.