Physiology of Adrenal Gland

Question 1

Which hormone is required to stimulate norepinephrine to epinephrine?

Answer 1

Cortisol

Question 2

Which amino acid is norepinephrine stimulated from?

Answer 2

Tyrosine-> Dopamine-> Norepinephrine

Question 3

Which substances are assessed in urine to clinically assess the level of catecholamine production in a patient?

Answer 3

Vanillylmandelic acid (VMA) and metanephrine

Question 4

Adrenal catecholamines are methylated by _______ in nonneuronal tissues such as the liver and kidney.

Answer 4

Catechol-O-methyltransferase (COMT)

Question 5

Pheochromocytoma

Answer 5

Benign tumor of the adrenal gland

Question 6

What factors can stimulate release of epinephrine?

Answer 6

Anxiety

Pain

Trauma

Hypovolemia

Hypoglycemia

Hypothermia

Question 7

Catecholamines require ________ and _______ to exert their full effects.

Answer 7

Thyroid hormone; cortisol

Question 8

Epinephrine and norepinerphrine ____________ (increase/decrease) blood flow to muscles.

Answer 8

Increase

Question 9

Epinephrine promotes _____________ (glycogenesis/glycogenolysis) in muscle.

Answer 9

Glycogenolysis

Question 10

Epinephrine and norepinephrine stimulate glucogon secretion and inhibit insulin secretion. Which receptor is used carry out each action, respectively?

Answer 10

B2: Stimulate glucagon secretion

A2: Inhit insulin secretion

Question 11

Catecholamines cause ___________ (relaxation/constriction) of bronchiolar smooth muscle.

Answer 11

Relaxation

*They also act to decrease energy demand by visceral smooth muscle

Question 12

Pro-opiomelanocortin (POMC) is a precursor for which hormones? What is the function of each?

Answer 12

α-MSH

• regulation of appetite
• production of melanin.

ACTH

• regulates the secretion of glucocorticoids from the adrenal cortex.

β-Endorphin and Met enkephalin

• endogenous opioid peptides with widespread actions in the brain.

Question 13

What are the major effects of cortisol at normal levels?

Answer 13

• Stimulates:
  
  • Gluconeogenesis​
    
    • ​Induces synthesis enzymes involved in hepatic gluconeogenesis
  • Protein catabolism
    
    • To provide substrate for glucogenesis​
  • Lipolysis
    
    • ​In adipise
  • Inhibition of insulin-stimulated glucose uptake by muscle and adipose tissue

REMEMEBER: Cortisol is considered a diabetogenic hormone

Question 14

Physiological actions of glucocorticoids

Answer 14

Question 15

Cortisol inhibits ______ that is activated in response to injury.

Answer 15

Prospholipase A2

Question 16

Cortisol decreases ______ migration to the site of injury.

Answer 16

Leukocyte

REMEMBER: Cortisol has immunosuprressive activity

Question 17

What are the different types of causes of Cushing’s syndrome?

Answer 17

ACTH-dependent

• Cushing’s disease (pituatary dependent)
• Ectopic ACTH syndrome
• Ectopic CRH syndrome

ACTH-independent

• Adrenal adenoma and carcinoma
• Iatrogenic

Pseudo-cushing’s syndrome

• Alcoholism
• Depression
• Obesity

Question 18

What are the major signs and symptoms of Cushing’s syndrome?

Answer 18

Central obesity

Increased body weight

Fatigabilty and weakness

Hypertension

Hirtuitism

Amennorhea

Cutaneous striae

Personality changes

Ecchymoses (bruises)

Proximal myopathy

Edema

Question 19

What are the symptoms that are more specific to Cushing’s syndrome?

Answer 19

Central obersity

Hirsuitism

Amenorrhea

Cutaneous striae

Ecchymoses

Proximal myopathy

Question 20

Dexamethasone suppresion test

Answer 20

• Assess the pituatary corticotroph cell response to glucocoticoid negative feedback on ACTH secretion.

NOTE: Dexamethasone is potent glucocorticoid, about 30 to 40 times more potent than cortisol

Question 21

How should the following results be interpreted?

• Low dose dexamethasone administered
• Decrease in cortisol levels

Answer 21

Normal

Question 22

How should the following results be interpreted?

• Low dose dexamethasone administered
• Cortisol is not suppressed by low doses
• ACTH is undetectable or low

Answer 22

Cushing’s syndrome (primary hypercortisolism)

• ​Cortisol is being released in high levels so even with feedback from the dexamethasone to the hypothalamus and pituatary, one small dose is not enough to lower cortisol levels.

Question 23

How should the following results be interpreted?

• High dose dexamethasone administered
• Cortisol is not suppressed by low doses, but is suppressed by high doses
• ACTH is normal to elevated

Answer 23

Cushing’s disease (Secondary hypercortisolism)

• Likely a pituatary adenoma
• ACTH is elevated

Question 24

How should the following results be interpreted?

• High dose dexamethasone administered
• Cortisol is not suppressed by high or low doses
• ACTH is elevated into hundreds

Answer 24

Ectopic ACTH syndrome

Question 25

What effect does aldosterone have on the following molecules? Sodium, Potassium, Hydrogen Ion, Bircarbonate, Water

Answer 25

* **Sodium** * increases reabsorption * **Potassium** * Increases secretion in colelcting duct * **Hydrogen Ion** * Increases secretion by intercalated cells of the collecting duct * **Bircarbonate** * Produces * **Water** * **​**Reabsoption

Question 26

Which hormones stimulate Na+/K+ ATPase in reponse to the rise in plasma K+

Answer 26

Insulin, aldosterone, and epinephrine **NOTE:** These hormones also stimulate Na+/K+/Cl= symporter and the Na+/Cl- symporter to **increases cellular uptake**. The kidneys then excrete excess K+

Question 27

How do high plasma potassium levels stimulate aldosterone secretion?

Answer 27

Increase in plasma K+ depolarizes the plasma membrane and opens voltage-gated Ca+ channels leading to **steroidogenesis** in the _glomerulosa_ of the adrenal cortex

Question 28

\_\_\_\_\_\_\_\_\_\_\_ binds to receptors in the zona glomerulosa and inhibits the synthesis of aldosteron.

Answer 28

ANP **REMEMBER:** ANP is released by the cardiac atrial muscle fibers in response to expansion of blood volume. It causes small increases in GFR and decreases sodium reabsorption at the collecting ducts

Question 29

Addison's disease

Answer 29

* The adrenal glands do not produce enough steroid hormones. * Low cortisol * Low aldosterone

Question 30

What are the causes of adrenal insuffiency?

Answer 30

* **Primary** * Destruction of gland * Metabolic * Congenital adrenal hyperplasia * **Secondary** * **​**Hypothalamic-pituatary disease * Suppression of HPA- exogenous steroids

Question 31

What are the signs and symptoms of adrenal insufficiency?

Answer 31

Weakness Pigmentation of skin Weight loss Anorexia, nausea, and vomiting Hypotension Pigmentation of mucus membranes Abdominal pain Diarrhea Syncope

Question 32

What is the most likely cause of polyuria?

Answer 32

Aldosterone escape

Question 33

Major cause of secondary hyperaldosteronism

Answer 33

Usually caused by over-secrection of renin secondary to a decrease in renal blood flow and/or pressure

Question 34

What are the major clinical symptoms of hyperaldosteronism?

Answer 34

* Increased whole body sodium, fluid, and circulating blood volume * Increase peripheral vasoconstriction and TRP * Borderline to severe hypertension * Edema rare * Hypokalemia