Endocrine System & Diseases Flashcards
What is paracrine signaling?
Signaling between local cells
What is autocrine signaling?
Signaling within the cell
What is endocrine signaling?
Between remote cells
What are some general characteristics of hormonal function/regulation?
- specific rates and rhythm of secretion
- operate within feedback systems
- only affects cells with appropriate receptors to initiate specific functions
- either excreted by kidney or metabolized by liver
What are the 3 mechanisms involved in the regulation of hormone release?
Chemical factors (blood sugar, calcium levels), endocrine factors (hormone from one gland controlling another gland), neural control
Identify and explain the most common type of feedback system.
Negative feedback system: plasma levels of one hormone influence the plasma levels of another hormone
Explain the negative feedback system involved in the hypothalamic-pituitary-adrenal axis.
Normal hormone release is as follows… Hypothalamus secretes corticotropin releasing hormone (CRH)…. Triggers release of adrenocorticotropic hormone release by the anterior pituitary… Cortisol levels increase…
When they exceeds a certain plasma level the negative feedback system triggers the hypothalamus to stop releasing CRH
Are peptide and protein hormones water or lipid soluble? What effect does this have on a hormone?
Peptide/Protein hormones are water soluble…and circulate in free/unbound form (only unbound hormones can affect the target site)
Lipid soluble hormones are primarily circulated bound to a carrier or protein (only small % are unbound)
Where are hormone receptors located and how do water soluble and lipid soluble hormones bind?
They are located on plasma membrane or in intra cellular compartments of the target cell; water soluble hormones bind to receptors on the cell membrane, while lipid soluble hormones (such as steroid hormones) easily diffuse across the cell membrane and bind either cytosolic or nuclear receptors
Does the pancreas function as an endocrine system… Or as an exocrine system?
Both!: as an endocrine system it secretes insulin, glucagon, somatostatin, and pancreatic polypeptide
As an exocrine system it is composed of acinar cells that secretes enzymes and networks of ducts that secrete alkaline fluids with digestive functions (80-85% of the pancreas)
The alkaline juices neutralize acidic chyme that enters the duodenum from the stomach and facilitates absorption of fat in the intestine
What is secreted from the alpha and beta cells of the pancreas?
Alpha cells secrete glucagon, beta cells secrete insulin
What is the primary cause of acute pancreatitis?
Gallstones and heavy alcohol use are responsible for 60-80%; other causes include infection, trauma, surgery, metabolic disorders (hypercalcemia, hyperlipidemia), some meds (flagyl, tetracycline, ace inhibitors, corticosteroids)
What is the primary cause of damage during periods of inflammation of the pancreas?
Digestive enzymes become activated before entering the duodenum and begin attacking the pancreas
What is acute necrotizing pancreatitis?
A severe form of pancreatitis characterized by necrosis and subsequent infection
Inflammation leads to necrosis which will typically become infected by gram negative bacteria in the alimentary tract….. Tissues become infected (acinar, ductal, islets of L)…. Vascular injury can lead to massive hemorrhage within the pancreas
What is the primary signs, symptoms, and patho of acute pancreatitis?
Midepigastric pain radiating to the back, n/v, abdominal distention, tetany (from hypocalcemia), fever, paralytic ileus, hypoxemia
Injury or disruption of acinar cells permits leakage of pancreatic enzymes—- breaks down tissue and cell membranes— causes inflammation, edema, vascular damage, necrosis….
What is the hallmark sign used for diagnosis of acute pancreatitis?
Elevated serum amylase level; but serum lipase is more specific and sensitive for the diagnosis of AP
What are the normal values for serum amylase and serum lipase?
Amylase 60-180u/L
Lipase 10-140u/L
3 times normal with acute AP
What is the goal of treatment for acute pancreatitis?
Stop auto digestion and prevent systemic complications
Aggressive fluid administration, Demerol over morphine (< sphincter of oddi spasm), bowel rest (NGT and TPN), h2 blocker, stone removal, antibiotics if necrotizing, surgery (ERCP, surgical debridement)
What is the patho and primary causes of chronic pancreatitis?
Chronic alcohol, smoking, obstruction from gallstones, autoimmune, obesity, genetic mutations
Toxic metabolites and chronic release of cytokines contribute to destruction of acinar cells and islets of langerhans—-> fibrosis structures, calcification, ductal obstruction, pancreatic cysts
What are the signs and symptoms of chronic pancreatitis? Preventative measures?
Abdominal pain (continuous or intermittent), weight loss, DM, steatorrhea (pooping excess fat d/t decreased absorption)
Lifestyle modification, fat free diet, enzyme replacement, surgical drainage or resection
What are some anesthetic considerations for patient with pancreatitis?
Consider RSI (aspiration), fluid and electrolyte disturbance, monitor glucose, check Coags, pulmonary assessment, monitor renal function (UOP > 0.5 ml/kg/hr
What 3 physiologic processes do thyroid hormones have the most profound effects?
Growth, development, metabolism
Explain the primary characteristics of T3 and T4. Compare and contrast.
T3 is primary made during the conversion of T4 at the target tissues. It only comprises 10% of the circulating thyroid hormone but is responsible for 80% of the metabolic activity due to its high potency.
T4 is secreted by the thyroid and makes up 90% of the circulating thyroid hormone.
Explain the regulation of thyroid hormone.
Stimulus such as hypothermia causes the hypothalamus to secrete thyrotropin releasing hormone (TRH) which signals the thyrotropic cells of the anterior pituitary to secrete thyroid stimulating hormone (TSH)….. TSH causes follicular cells of the thyroid to release thyroid hormone….TH stimulates target cells to increase metabolic activity, resulting in an increase in body temperature….. Increased temperature is detected by the hypothalamus which discontinues release of (TRH)…. TH also blocks the ability of TRH to interact with the anterior pituitary gland to prevent TSH formation….. This is a type of negative feedback system
The ability of the thyroid to have normal quantities of thyroid hormones depends on what source?
Exogenous iodine
What are normal serum TSH levels?
0.5-5 mu/L; small changes in thyroid function causes significant changes in TSH; single best test of thyroid hormone action at the cellular level
What are some signs and symptoms of hypothyroidism?
Weight gain, cold intolerance, muscle fatigue/weakness, constipation, depression, decreased CO, SV, HR, contractility
What is the concern with severe hypothyroidism?
Myxedema coma… From extreme hypothyroidism…. Impaired mentation, hypo ventilation, CHF, hypothermia
When is it appropriate to place a PA catheter for resection of a pheochromocytoma?
In presence of CHF or decreased cardiac reserve; monitor pulmonary capillary wedge pressure
What is the purpose of the alpha adrenergic blockade in a pheochromocytoma case?
BP reduction/control and to assist with vascular relaxation to allow volume expansion
Why is a high sodium diet recommended after the second or third day of alpha blockade, and when is it contraindicated?
To assist in volume expansion with adequate alpha blockade; contraindicated in presence of CHF and renal insufficiency
Why should beta blockade never be initiated before alpha blockade?
Because blockade of vasodilatory peripheral beta receptors with unopposed alpha adrenergic receptor stimulation can lead to further elevation in BP
What would be the primary differential diagnosis if your patient experiences acute pulmonary edema after initiation of beta blockade?
Underlying catecholamine excess cardiomyopathy
If a patient experiences intolerable side effects with alpha blockade, what drug class can be used in its place or as a supplement?
CCB’s
What is the role of metyrosine in preparation for pheochromocytoma surgery?
Inhibits catecholamine synthesis; a study showed patients given metyrosine had smoother intra op course than those receiving phenoxybenzamine alone; most reports state to use it with caution only when other preop methods are not tolerated or ineffective; according to short term therapy used by Mayo, the main side effect is hyper somnolence
What curative treatment options are available for malignant pheochromocytoma?
No curative treatment unless sites of the disease are surgically resectable
What is an appropriate medication to give preop if your patient is planned to have a bilateral adrenalectomy?
Glucocorticoid stress coverage
According to one article, what risk factors are associated with increased incidence of intra op hypertensive events?
Higher preop norepinephrine plasma concentration, larger tumor size >4cm, more pronounced postural BP fall after alpha blockade (>10mmhg)
What drugs can be used intraoperatively with the occurrence of a hypertensive crisis associated with a pheochromocytoma?
IV sodium nitroprusside (ideal vasodilator….rapid onset and short duration…0.5-5mcg/kg/min…prolonged infusion no more than 3mcg/kg/min), phenolamine (short acting non-selective alpha adrenergic blocker…initial test dose of 1mg followed by repeat 5mg bolts or infusion…bolus lasts about 10-15 min), or nicardipine (CCB… Can start at 5mg/hour…titration to max of 15mg/hr)
Why can hypoglycemia occur after a thyroidectomy or removal of a pheochromocytoma?
Catecholamines suppress insulin secretion…. So removal of surplus Catecholamines will stop suppression of insulin… Thus causing potential for hypoglycemia?
What is the classic triad of pheochromocytoma?
Episodic headache, sweating, and tachycardia in association with hypertension
In the case of pheochromocytoma, a patient with MEN2 and evidence of bilateral disease on imaging should receive what type of surgical intervention?
Bilateral adrenalectomy d/t risk of recurrent pheochromocytoma
In the case of pheochromocytoma, a patient with VHL and evidence of bilateral disease on imaging should receive what type of surgical intervention?
VHL is a less diffuse medullary disease…. Suggest cortical sparing bilateral adrenalectomy… D/t risk of recurrence, long term biochemical monitoring is suggested
What is the suggested surgical intervention for patient with MEN2 or VHL with unilateral pheochromocytoma?
Unilateral adrenalectomy…. Then annual biochemical testing for contralateral pheochromocytoma
Just some information on complications that are associated with diabetic patients:
Heart disease 68%, hypertension 67%, nervous system 60-70%, amputations 60% of all non-traumatic cases, stroke 16%, kidney disease
What is the general definition of diabetes?
A disease process that results in either an inadequate production of insulin, or inadequate tissue response to insulin
Describe the process of blood glucose homeostasis that is maintained by the pancreas and liver upon consuming food.
Blood sugar rises…. Beta cells of pancreas secrete insulin into the blood…muscle and other cells use this glucose as energy or converts it to glycogen…liver converts glucose into glycogen, fats, and protein… Homeostasis is achieved when blood glucose is < 110mg/DL