Physiology of Adrenal Gland Flashcards
Which hormone is required to stimulate norepinephrine to epinephrine?
Cortisol
Which amino acid is norepinephrine stimulated from?
Tyrosine-> Dopamine-> Norepinephrine
Which substances are assessed in urine to clinically assess the level of catecholamine production in a patient?
Vanillylmandelic acid (VMA) and metanephrine
Adrenal catecholamines are methylated by _______ in nonneuronal tissues such as the liver and kidney.
Catechol-O-methyltransferase (COMT)
Pheochromocytoma
Benign tumor of the adrenal gland
What factors can stimulate release of epinephrine?
Anxiety
Pain
Trauma
Hypovolemia
Hypoglycemia
Hypothermia
Catecholamines require ________ and _______ to exert their full effects.
Thyroid hormone; cortisol
Epinephrine and norepinerphrine ____________ (increase/decrease) blood flow to muscles.
Increase
Epinephrine promotes _____________ (glycogenesis/glycogenolysis) in muscle.
Glycogenolysis
Epinephrine and norepinephrine stimulate glucogon secretion and inhibit insulin secretion. Which receptor is used carry out each action, respectively?
B2: Stimulate glucagon secretion
A2: Inhit insulin secretion
Catecholamines cause ___________ (relaxation/constriction) of bronchiolar smooth muscle.
Relaxation
*They also act to decrease energy demand by visceral smooth muscle
Pro-opiomelanocortin (POMC) is a precursor for which hormones? What is the function of each?
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.
What are the major effects of cortisol at normal levels?
- 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
-
Gluconeogenesis
REMEMEBER: Cortisol is considered a diabetogenic hormone
Physiological actions of glucocorticoids
Cortisol inhibits ______ that is activated in response to injury.
Prospholipase A2
Cortisol decreases ______ migration to the site of injury.
Leukocyte
REMEMBER: Cortisol has immunosuprressive activity
What are the different types of causes of Cushing’s syndrome?
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
What are the major signs and symptoms of Cushing’s syndrome?
Central obesity
Increased body weight
Fatigabilty and weakness
Hypertension
Hirtuitism
Amennorhea
Cutaneous striae
Personality changes
Ecchymoses (bruises)
Proximal myopathy
Edema
What are the symptoms that are more specific to Cushing’s syndrome?
Central obersity
Hirsuitism
Amenorrhea
Cutaneous striae
Ecchymoses
Proximal myopathy
Dexamethasone suppresion test
- 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
How should the following results be interpreted?
- Low dose dexamethasone administered
- Decrease in cortisol levels
Normal
How should the following results be interpreted?
- Low dose dexamethasone administered
- Cortisol is not suppressed by low doses
- ACTH is undetectable or low
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.
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
Cushing’s disease (Secondary hypercortisolism)
- Likely a pituatary adenoma
- ACTH is elevated
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
Ectopic ACTH syndrome
What effect does aldosterone have on the following molecules?
Sodium, Potassium, Hydrogen Ion, Bircarbonate, Water
-
Sodium
- increases reabsorption
-
Potassium
- Increases secretion in colelcting duct
-
Hydrogen Ion
- Increases secretion by intercalated cells of the collecting duct
-
Bircarbonate
- Produces
-
Water
- Reabsoption
Which hormones stimulate Na+/K+ ATPase in reponse to the rise in plasma K+
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+
How do high plasma potassium levels stimulate aldosterone secretion?
Increase in plasma K+ depolarizes the plasma membrane and opens voltage-gated Ca+ channels leading to steroidogenesis in the glomerulosa of the adrenal cortex
___________ binds to receptors in the zona glomerulosa and inhibits the synthesis of aldosteron.
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
Addison’s disease
- The adrenal glands do not produce enough steroid hormones.
- Low cortisol
- Low aldosterone
What are the causes of adrenal insuffiency?
-
Primary
- Destruction of gland
- Metabolic
- Congenital adrenal hyperplasia
-
Secondary
- Hypothalamic-pituatary disease
- Suppression of HPA- exogenous steroids
What are the signs and symptoms of adrenal insufficiency?
Weakness
Pigmentation of skin
Weight loss
Anorexia, nausea, and vomiting
Hypotension
Pigmentation of mucus membranes
Abdominal pain
Diarrhea
Syncope
What is the most likely cause of polyuria?
Aldosterone escape
Major cause of secondary hyperaldosteronism
Usually caused by over-secrection of renin secondary to a decrease in renal blood flow and/or pressure
What are the major clinical symptoms of hyperaldosteronism?
- Increased whole body sodium, fluid, and circulating blood volume
- Increase peripheral vasoconstriction and TRP
- Borderline to severe hypertension
- Edema rare
- Hypokalemia
