Clin Med Deck Adrenal disorders Flashcards
What are the three layers to the adrenal cortex?
Zona glomerulosa, Zona fasciculata, and zona reticularis
What does the zona glomerulosa make? What do they do? Example?
Zona glomerulosa makes mineralcorticoids Mineralcorticoids regulate blood pressure and electrolyte homeostasis. An example of this is aldosterone.
What does the zona fasciculata make? Example? What do they do?
Zona fasiculata produces glucocorticoids Glucocorticoids regulate the stress response, immune system, and metabolism. An example of this is cortisol, corticosterone, and cortisone.
What does the zona reticularis make? What do they do? Example?
Zona reticularis produces androgens. These are converted to sex steroids such as testosterone, An example of this is DHEA - can be thought of as an intermediate to sex steroids.
What’s a mnemonic to help remember the layers of the adrenal cortex?
Go find Rex - Zona Glomerulosa, Zona fasciculata, zona reticularis Make good sex - Mineralcorticoids, glucocorticoids, (sex hormones)/androgens
What does the adrenal medulla make?
The adrenal medulla makes catecholamines such as epinephrine and norepinephrine. It also makes a small amount of dopamine
What does aldosterone do? What is production stimulated by?
Aldosterone is mineralcorticoid. It is synthesized from cholesterol.
Aldosterone is secreted whenever there is an increase in potassium in the blood. It is also stimulated by angiotensin II whenever there is low blood volumes.
Aldosterone works on the distal convoluted tubules and collecting ducts and works to reabsorb sodium and excretes potassium and hydrogen. This effectively leads to water retention which would lead to increase in blood pressure. It works in the renin-angiotensin-aldosterone system.
Describe the Renin-Angiotensin-Aldosterone system in steps
1) The Renin-Angiotensin-Aldosterone system is stimulated by a Sodium deficiency, dehydration, or hemorrhage
2) Na+ deficiency, hemorrhage, or dehydration all equate to decrease in blood volume
3) A decrease in blood volume equates to a decrease in blood pressure
4) A decrease in blood pressure is sensed by the juxtaglomerular cells of the kidney
5) In a response from the decrease in blood pressure, the juxtaglomerular cells will secrete renin.
6) Not only if renin produced but angiotensinogen is then also produced by the liver. Any angiotensinogen floating around in the blood stream is then turned into angiotensin 1 via renin.
7) Angiotensin 1 then goes to the lungs
8) The lungs have high amounts of angiotensin converting enzyme so they convert angiotensin 1 into angiotesin II.
9) Angiotensin II is one of the molecules that has effects on the body. It will directly cause vasoconstriction of arterioles increasing blood pressure, it will also go to the adrenal cortex to stimulate the release of aldosterone.
10) The release of aldosterone causes sodium reabsorption into the blood stream and then causes the excretion of potassium and hydrogen ions.
11) The increase in sodium in the bloodstream will effectly increase water reaborption which in turn increase blood volume. An increase in blood volume will increase blood pressure.
12) In summary, the Renin-angiotensin-aldosterone system works by detecting low amounts of sodium, dehydration, or hemorrhage and works to increase blood volume and blood pressure via angiotensin II - causing constriction of arterioles, and stimulating aldosterone which works by increasing sodium reabsorption and increasing blood volume in turn increasing blood pressure.
What is the function of cortisol? When is it released? What does it do to glucose?
Cortisol is the main glucocorticoid in humans. Cholesterol is the precursor to cortisol
It is released in response to stress and low blood glucose. It effectively increases the circulating level of glucose via stimulating gluconeogenesis and playing a smaller role in glycolysis.
It decreasese the absorption of calcium in the GI tract, and decreases the capacity of osteoblasts to produce new bone tissue.
Cortisol also has the effect of supressing the immune system, and works as an anti-inflammatory.
When is cortisol highest? What is the circadian rhythym of cortisol?
Cortisol is highest in the morning around 8 am. You can think of waking up as stimulating a lot of cortisol.
The lowest amount of cortisol is in the evening. This is due to the circadian rhythym of ACTH which is the hormone secreted from the pituitary gland that tells the adrenal cortex to secrete cortisol.
Describe the hypothamic-pituitary-adrenal axis
The hypothalamus detects levels of cortisol in the body. Cortisol has a negative feedback on the hypothalamus. But when there are low levels of cortisol the hypothalamus will secrete cortiotropin-releasing hormone.
Corticotropin releasing hormone will go to the anterior pituitary and act on the ant pit to release ACTH. ACTH is then released and goes to the adrenal glands. Cortisol also has negative feedback on the anterior pituitary.
The ACTH acting on the adrenal glands works by causing the release of cortisol. If we remember, cortisol is a glucocorticoid and is released by the zona fasciculata.
What does DHEA do? Where is it secreted?
DHEA (didehydroepiandrosterone) is produced from cholesterol and serves as the precursor for sex steroid hromone synthesis.
It is a steroid hormone that acts and binds to activate estrogen, testosterone and DHT.
It is secreted by the zona reticularis.
What does epinephrine do? Where is it secreted?
Epinephrine is also known as adrenaline and is secreted from the medulla of the adrenal glands.
- It is a hormone that is an agonist of adrenergic receptors (sympathetic nervous system) and causes a vareity of differenet effects known as the fight or flight response.
- These effects are increasing heart rate
- increasing respiratory rate
- stimulating glycogenolysis and lipolysis
- Stimulating muscle contraction
- vasoconstriction and vasodilation depending on where in the body.
What does norepinephrine do? where is it secreted?
Norepinephrine is also known as norardenaline and is also secreted in the medula of the adrenal gland.
- It is a hormone and neurotransmitter that activates noradrenergic receptors and also plays a role in the fight or flight response
- it serves to increase arousal and alertness in the brain
- helps forming and retrieivng memories
- increases restlessness and anxiety
- it increases BP and heart rate.
- It triggers the release of glucose from stores
- it increases blood flow to skeletal muscle
- it decreases gi motility, urination, and blood flow to the gi tract.
What are the effects we would see in hyperaldosteronism?
Remember, aldosterone works to increase sodium reabsorption in the kidneys and works to increase secretion of potassium and hydrogen ions
Therefore, if there was too much we would see a decrease in potassium resulting in hypokalkemia, an increase in sodium resulting in hypernatremia, and an increase in blood pressure. “classic findings are hypokalemic, hypernatremic, metabolic alkalosis”
This is from an overproduction of aldosterone by the adrenal cortex. (specifically the zona glomerulosa). This may be primary or secondary.