Mineralocorticoids Flashcards
Mineralocorticoids
synthesized in zona ???
glomerulosa
regulate the electrolyte concentration of extracellular fluids
Mineralocorticoids
- most important mineralocorticoid
Aldosterone
Maintains Na+ balance by reducing excretion of sodium from the body
Stimulates reabsorption of Na by the kidneys and K+ excretion
Aldosterone
Expands ECF volume
Aldosterone
Aldosterone secretion is stimulated by:
Decreasing blood volume or pressure (renin-angiotensin system) is the major stimulant
Low blood Na+
Rising blood levels of K+
ACTH
The Four Mechanisms of Aldosterone Secretion
RPAA
Renin-angiotensin mechanism
Plasma concentration of sodium and potassium
ACTH
Atrial natriuretic peptide (ANP)
Renin-angiotensin mechanism
- kidneys release_____, which is converted into ______that in turn stimulates aldosterone release
renin
angiotensin II
- directly influences the zona glomerulosa cells
Plasma concentration of sodium and potassium
- causes small increases of aldosterone during stress
ACTH
- inhibits activity of the zona glomerulosa
Atrial natriuretic peptide (ANP)
Actions of Aldosterone
Stimulates sodium reabsorption by ______ and ______of the nephron and promotes potassium and hydrogen ion excretion
Increases transcription of Na/K pump
Increases the expression of apical Na channels and an Na/K/Cl cotransporter
distal tubule and collecting duct
Ag-Il will act on….
ADH - water reabsorption
Thirst - increased
Arteriolar vasoconstriction- increased
Aldosterone - increased sodium reabsorption and potassium excretion
Aldosterone: Role in Diseases
Complete failure to secrete aldosterone leads to ______ why??
DEATH
dehydration, low blood volume
Hyperaldosterone states
• Contribute to_____ associated with increased blood volume.
hypertension
Role in Diseases
Overproduction of Aldosterone
(i.e., Conn’s syndrome) adenoma, nodular hyperplasia of zona glomerulosa
Primary causes
Role in Diseases
Overproduction of Aldosterone
cirrhosis, ascites, nephrotic syndrome
Secondary causes
there is a unilateral adenoma (benign tumor) of the adrenal gland, causing a condition known as hyperaldosteronism
Conn’s syndrome
Conn’s syndrome
there is a unilateral adenoma (benign tumor) of the adrenal gland, causing a condition known as______
hyperaldosteronism
when both adrenal glands are making too much aldosterone, the condition is called________
bilateral adrenal hyperplasia
bilateral adrenal hyperplasia vs conn’s syndrome
Conn’s - one adrenal gland is affected
Bilateral adrenal hyperplasia - both adrenal glands
Overproduction of Aldosterone
• Treatment
• surgical for adenoma
• medical for hyperplasia (Spironolactone)
an enlargement of an adrenocorticotropic hormone-producing tumor in the pituitary gland, following surgical removal of both adrenal glands
Nelson’s Syndrome
PA/PRA Ratio:
• PA =
• PRA =
• A PA/PRA ratio_____is suggestive of primary aldosteronism (PA).
Plasma Aldosterone
Plasma Renin Activity
> 25
Low Renin:
• In primary aldosteronism, renin levels remain_____ and fail to rise even when the body experiences volume depletion (e.g., dehydration).
High Aldosterone:
• Aldosterone levels remain____ and are not suppressed by:
• Saline infusion (which normally lowers aldosterone).
• Angiotensin inhibition.
low
high
Upright PA/PRA Ratio Test
• Why it’s done: To measure the PA/PRA ratio under two conditions. • Steps:
- Fluid deprivation: Overnight dehydration _______in normal individuals, but PRA stays low in primary aldosteronism.
- Volume expansion: After 2 liters of saline over 4 hours, aldosterone secretion is______ in normal individuals. In PA, it remains high.
increases PRA (renin levels)
suppressed
• Purpose: Screens for excessive aldosterone activity based on how much potassium is excreted in urine.
Urinary Potassium Excretion Test
Urinary Potassium Excretion Test
• Results:
•_________ : Suggests primary aldosteronism (excess aldosterone causes K⁺ loss in urine).
• _________: Indicates other causes, such as diuretic use or gastrointestinal potassium loss.
> 30 mEq/day
<30 mEq/day
Confirms aldosteronism by testing if aldosterone levels can be suppressed.
Captopril Suppression Test
Captopril Suppression Test
• Steps:
1. Take_____ of____ orally.
2. Measure aldosterone levels at baseline, 1 hour, and 2 hours post-captopril.
Results:
• High aldosterone levels: Confirms______.
• Suppressed aldosterone: Points to other causes of high blood pressure.
50 mg; captopril
aldosteronism
Additional Confirmatory Tests
: Tests if a high sodium diet suppresses aldosterone.
: Administers saline to suppress aldosterone.
: Uses a synthetic mineralocorticoid to evaluate aldosterone secretion.
Oral Sodium Loading Test
Saline Infusion Test
Fludrocortisone Suppression Test
Results:
•______: Suggests either:
• Aldosterone-producing adenoma (APA).
• Idiopathic hyperaldosteronism (IHA).
18-Hydroxycorticosterone Measurement
> 100 ng/dL
to detect tumors or hyperplasia
CT scan or MRI
to detect tumors or hyperplasia
CT scan or MRI
ACTH
• Pulsatile fashion
Diurnal variation
• Highest -
• Lowest -
• Protein-rich meals
2:00 am - 4:00 am
8:00 am
10:00 pm - 12 mn
