Endocrine Function III: Adrenal Cortex and Adrenal Medulla Hormones Flashcards
Basic anatomy of the adrenal cortex
- Capsule (outer)
- Adrenal cortex
- Adrenal medulla (inner)
Three layers of the adrenal cortex
- Zona glomerulosa (outermost)
- Zona fasciculata (middle)
- Zona reticularis (innermost)
Three major hormone classes of the adrenal cortex
- Estrane
- Andosane
- Pregnane
Major hormone(s) produced by the zona glomerulosa layer
Mineralocorticoids
Major hormone(s) produced by the zona fasciculata layer
Glucocorticoids
Major hormone(s) produced by the zona reticularis layer
Sex hormones
Number of carbons on estrogens, androgens, and adrenal steroids
- Estrogens: 18
- Androgens: 19
- Adrenal steroids: 21
First biosynthetic pathway for adrenocorticosteroid formation
Acetate → Cholesterol → Pregnenolone → Adrenocorticoids
Second biosynthetic pathway for adrenocorticosteroid formation (not preferred)
Pregnenolone → DHEA → Androstenedione → Testosterone → (Estradiol)
Causes of adrenocorticosteroids utilizing alternate pathway instead of the preferred pathway
Enzyme deficiencies
Importance of enzymes in steroid biogenesis
Takes enzymes to make conversions to final product
Major site of steroid metabolism
Liver
Form of adrenocorticosteroids excreted in the urine
- Liver is the site of catabolism
- Water-insoluble hormones must be conjugated w/ sulfates or glucuronic acid to be excreted in urine
Which steroid has a negative feedback effect on adrenocorticotrophic hormone (ACTH)
Cortisol
Name of the principle cortisol-binding protein
CBG
Mineralocorticoids
- Metabolic effects
- Maintain sodium and potassium balance
- Aldosterone
Four regulatory factors for aldosterone secretion (order of importance)
- Potassium concentration
- RAAS
- Total body sodium concentration
- ACTH (has minor effect unless ACTH is pathologically in excess or is deficient)
Glucorticoids
- Metabolic effects
- Promotion of gluconeogenesis and lipolysis
- Promotion of liver glycogenesis
- Promotion of liver glycogenolysis
- Inhibition of protein synthesis and promotion of protein catabolism
- ↑ anti-inflammatory and immunosuppressive action
- ↓ intestinal absorption of Ca2+; ↑ loss of Ca2+ from bone matrix
- Miscellaneous: enzyme production, appetite promotion, regulation of blood pressure
Most potent glucocorticoid
Cortisol
Most potent mineralocorticoid
Aldosterone
Most potent adrenocortical androgen
Testosterone
What is the role of RAAS on the regulation of aldosterone?
Releases aldosterone and reabsorbs Na+ and releases K+
Three regulatory factors for the release of glucocorticoids
- ACTH stimulation of hormone
- Normal diurnal variation
- Stress
Feedback mechanism utilized in glucocorticoid hormonal regulation
Cortisol causes negative feedback on hypothalamus and anterior pituitary
Normal diurnal variation in cortisol
- While sleeping, cortisol is very low so negative feedback is removed
- ACTH is released and there is a sharp ↑ while waking up (BP and sugar ↑ so you don’t pass out)
The cortisol levels ↓ over the day - By 4pm it should be 1/3 the level it was at 8am
What androgen is produced in the greatest quantity by the adrenal cortex?
Testosterone
Six conditions associated w/ a hypofunctioning adrenal cortex
- Primary hypoaldosteronism
- Secondary hypoaldosteronism
- Addison’s disease
- Acute adrenal insufficiency
- Secondary and tertiary adrenal insufficiency
Differentiate causes of primary hypoaldosteronism
Inability to adjust to stress, low Na+, high K+, high renin, low aldosterone
Differentiate causes of secondary hypoaldosteronism
Occurs in patient w/ renal disease,
- Kidney is unable to produce and release renin and therefore cause low aldosterone
List the typical sodium, potassium, and renin levels observed in hypoaldosteronism
- Low Na+
- High K+
- High renin
Addison’s disease
- Clinical symptoms due to glucocorticoids deficiency
- Fatigue
- Weakness
- Weight loss
- GI disturbances
- Post-parandial hypoglycemia
Addison’s disease
- Clinical symptoms due to mineralacorticoid deficiency
- Dehydration
- Hypotension
- Hyperkalemia
- Metabolic acidosis (↓H+ secretion)
- Hyponatremia (↓Na+ reabsorption into blood)
Addison’s disease
- Reason for hyperpigmentation and infertility
No negative feedback on anterior pituitary (e.g., hyperpigmentation present b/c excess ACTH stimulates MSH production)
Addison’s disease
- Na
- K
- Blood sugar
- Cortisol
- ACTH
- ↓ Na+
- ↑ K+
- ↓ Blood sugar
- ↓ Cortisol
- ↑ ACTH
What is the cause of the Addisonian crisis?
During infection or acute stress, Addison’s patient cannot respond with ↑ aldosterone and cortisol and can go into shock with hypotension, fever, hypovolemia, and hyperkalemia (life threatening)
What is the cause of Waterhouse-Friderichsen?
Caused by meningococcal meningitis and septicemia; this causes acute adrenal insufficiency