Endocrine System Flashcards
Adrenal Medulla?
Preganglionic SNS neurons release ACh, which binds to nicotinic receptors of adrenal medullary cells –> stimulating the secretion of catecholamines (80% EPI, 20% NE)
What are the effects of Aldosterone?
- enhances sodium reabsorption in exchange for K+ and H+
- The net effect is fluid retention and expansion of the extracellular space, with a reduction in serum potassium concentration and metabolic alkalosis.
- Regulates intravascular volume
What stimulates Aldosterone release?
- Angiotensin II
- Hyperkalemia
- Hyponatremia
- Increased ACTH (minor influence)
What is Conn Syndrome?
Mineralocorticoid excess / Hyperaldosteronism
The HPA (Hypothalamus-Pituitary-Adrenal Axis) is stimulated by …?
surgery, trauma, burns, exercise
What is the normal endogenous production of cortisol in non-stressed conditions?
15-30 mg/day (Normal is 20 mg/day)
Stress increases cortisol output to …?
60-100 mg/day
Name 5 actions of cortisol.
- Facilitates conversion of NE to EPI in adrenal medulla, inhibits production of endothelial prostacyclin (PGI2) responsible for vasodilation
- Retention of Na and excretion of K
- Enhances gluconeogenesis from protein breakdown and lipolysis
- Inhibits peripheral glucose utilization
- Anti-inflammatory and anti-allergic effects
What is Cushing’s Disease?
A tumor/adenoma in the pituitary gland that produces large amounts of ACTH, which in turn elevates cortisol levels
What is Cushing’s syndrome?
Most commonly caused by the administration of glucocorticoids used to treat other diseases
Ectopic ACTH syndrome - ACTH production by a nonpituitary tumor ex. Small Cell Lung carcinoma
What is adrenal insufficiency?
- the destruction of all of the cortical zones - decreased production of mineralocorticoids, glucocorticoids, and androgens.
- Adrenal insufficiency is a chronic state, but can deteriorate into acute adrenal crisis if the patient is faced with additional stress (infection, illness, sepsis, or surgery)
What is Primary adrenal insufficiency (Addison’s)?
- the adrenal glands don’t secrete enough steroid hormone
- cause: autoimune destruction of both adrenal glands (most common), HIV, TB
What is Secondary adrenal insufficiency?
- decreased CRH or ACTH release
- cause: exogenous steroid administration (most common) or HPA disease d/t tumor, infection, surgery, radiation
Exogenous steroid supplementation suppresses…?
- ACTH release from the anterior pituitary gland
- Some patients on chronic steroid therapy won’t be able to increase cortisol release in response to perioperative stress.
What patients require stress-dose steroids for surgery?
All patients who have received suppressive doses _>20mg Cortisol for 5 days-2 weeks in the last 12 months
Minor surgeries should receive _____mg Hydrocortisone dose?
25 mg IV
Moderate surgeries should receive _____mg Hydrocortisone dose?
50-75 mg IV
Major surgeries should receive _____mg Hydrocortisone dose?
100-150 mg IV
What does “High Powered MD - 20-5-4-1” stand for?
Hydrocortisone - 20 mg
Prednisone/Prednisolone - 5 mg
Methylprednisolone - 4 mg
Dexamethasone - 1 mg
Name the steps in catecholamine synthesis.
Tyrosine-(tyrosine hydroxylase)-DOPA-(DOPA decarboxylase)-Dopamine-(dopamine-B-hydroxylase)-Norepinephrine-(PMN)-Epinephrine
What is a Pheochromocytoma?
Catecholamine-secreting tumors of the sympathetic nervous system
*originate either in the adrenal medulla of a single adrenal gland or are extra-adrenal located in chromaffin tissue
The average pheochromocytoma contains how much NE?
100-800 mg
What is the classic triad of symptoms for Pheochromocytoma?
paroxysmal HTN, diaphoresis, palpitations
What chemical will be found in the urine of NE secreting Pheochromocytomas?
Vanillylmandelic acid
