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
What chemical will be found int he urine of EPI secreting Pheochromocytomas?
Metanephrine
The posterior pituitary is known as _____?
Neurohypophysis
The posterior pituitary secretes:_______?
ADH and Oxytocin
The anterior pituitary is known as:______?
Adenohypophysis
The anterior pituitary secretes:_____?
"FLAT PiG" ACTH TSH FSH LH GH Prolactin
What is Neurogenic (Central) DI?
Not enough ADH is synthesized
What is Nephrogenic DI?
The renal tubules and collecting ducts become resistant to vasopressin
What is an anesthesia consideration for pts with Acromegaly?
Use a smaller ETT than usual d/t airway narrowing
What is Carcinoid Syndrome?
Symptoms caused by the secretion of vasoactive substances from enterchromaffin cells. Usually associated with tumors of the GI tract.
*When hepatic function is normal, carcinoid hormones are cleared by the liver; when significant liver dysfunction occurs, these hormones are not cleared by the liver, they enter systemic circulation and cause systemic effects.
What substances are secreted by carcinoid tumors?
Serotonin
Kinins and Kallikriens
Histamine
What are the most common S/S of Carcinoid Syndrome?
Flushing and diarrhea
How is carcinoid Syndrome diagnosed?
The presence of serotonin metabolites in urine or elevated plasma levels of chromogranin A
What drug can be administered in carcinoid syndrome?
- Somatostatin (Octreotide or lanreotide): inhibits the release of vasoactive substances from carcinoid tumors
- Antihistamines
- 5-HT3 antagonists
- Steroids
What is Obesity Hypoventilation Syndrome (Pickwickian Syndrome)?
- The respiratory center in the medulla fails to respond to hypercarbia appropriately
- long-term consequence of untreated OSA
- Classic presentation: Episodes of apnea during sleep without any respiratory effort
What comprises the adrenal cortex and what does each layer secrete?
- zona glomerulosa - aldosterone (mineralocorticoids)
- zona fasciculata - cortisol (glucocorticoids)
- zona reticularis - androgens
How is OHS diagnosed?
BMI > 30
Awake PaCO2 > 45 mmHg
Dysfunctional breathing during sleep
The adrenal gland requires _____, which is then converted biochemically into steroid hormones.
cholesterol
What is the most common steroid synthesis problem?
Congenital adrenal hyperplasia
Various forms (21-hydroxylase, 17 a -hydroxylase, 11 b -hydroxylase, 3b-hydroxysteroid dehydrogenase)
What medications interfere with steroid synthesis enzymes?
ketoconazole
What medications accelerate the normal breakdown of hormones by the liver?
rifampicin, phenytoin
How does etomidate suppress adrenal function?
By inhibiting enzymes essential for production of corticoid steroid hormones
What is the cosyntropin provocative testing of the HPA?
A synthetic ACTH is administered to assess the ability of the adrenal gland to accelerate production of cortisol.
- Baseline cortisol levels are drawn (normal 6-18 ug/dL)
- Administer 0.25 mg of cosyntropin
- Draw cortisol levels at 30 min and 1 hour
- Responders >9, Nonresponders
Why do we give stress-dose steroids in anesthesia?
Blood pressure
What is the most frequent cause of death for Pheochromocytoma pts postop?
Hypotension - require large volumes of fluid because peripheral vasculature is unresponsive to the lover catecholamine levels
What is the function of ADH?
Controls water secretion and extracellular fluid osmolality
Controversially more potent vasoconstrictor than angiotensin II
What is the function of Oxytocin?
promotes milk letdown and uterine smooth muscle contraction
What medication is sometimes given in central DI?
Carbamazepine
