Endocrine Flashcards
Growth Hormone is released by?
Anterior Pituitary
GH
growth-promotion of tissues
direct anti-insulin actions
GH causes metabolic actions at adipose tissue and muscle, additionally a major target of GH is the liver where it stimulates the liver to produce somatomedin C also called IGF-1.
Imbalanced action of GH and IGF-1 can cause anatomical changes and metabolic dysfunction.
GH metabolic effects
- gluconeogenesis (increase blood sugar) & antagonism of insulin action
- increased rates of protein synthesis
- increased lipolysis/AA breakdown
- sodium and water retention
Gonadotropes
LH
FSH
ACTH
- stimulates adrenal cortex secretion and growth
- steriod production
Anterior pituitary hormones
Growth hormone (GH) Prolactin (PRL) Gonadotropins, including luteinizing hormone (LH) and follicle-stimulating hormone (FSH) Adrenocorticotrophic Hormone (ACTH) Thyroid-stimulating hormone (TSH)
precursor: B-lipotropin
Posterior Pituitary hormones
arginine vasopressin
oxytocin
arginine vasopressin
promotes H2o retention & regulates plasma osmolarity
oxytocin
causes ejection of milk and uterine contraction
prolactin
stimulates the secretion of milk and maternal behavior, inhibits ovulation
LH
stimulates ovulation in females and testosterone secretion in males
FSH
stimulates ovarian follicle growth in females and spermatogenesis in males
TSH
stimulates thyroid secretion and growth
B-lipotropin
precursor of endorphins
Body homeostasis is controlled by two major regulating systems:
- nervous system
2. endocrine & hormones
The endocrine system is evaluated by measuring ____ that are regulated ______
hormones
usually by a negative feedback system
Hormones can be classified into three major categories:
(1) proteins or peptides
(2) tyrosine amino acid derivatives
(3) steroids
The synthesis and secretion of hormones by endocrine glands are regulated by three general control mechanisms:
1) neural controls (stress response, pain, smell, touch, sight, taste)
2) biorhythms (circadian, seasonal, life stages)
3) feedback mechanisms (negative feedback)
Anesthetic Implications of Acromegaly
- facial deformities make masking difficult
- difficult DL d/t large thick tongue, enlarged thyroid, hypertrophy of epiglottis
- CV complications - HTN, cardiomyopathy
- coexisting OSA, osteoarthritis, kyphosis
- impaired HPA axis
Hormones of the Hypothalamus
Thyrotropin-releasing hormone (TRH)
Corticotropin-releasing hormone (CRH)
Growth hormone releasing hormone (GHRH)
Growth hormone inhibitory hormone (GHIH) (Somatostatin)
Gonadotropin-releasing hormone (GnRH)
Dopamine or prolactin-inhibiting factor (PIH)
ACTH
affects the release of adrenal androgens by the adrenal cortex in the zona reticularis
Pathophys of the Anterior Pituitary
acromegaly gigantism dwarfism sex hormone imbalance Secondary Cushing disease ( r/t excess ACTH)
Pathophys of the Posterior Pituitary
DI
SIADH
Recurrent Laryngeal Nerve Sensory/Motor functions
- Sensory innervation below true cords and into upper trachea
- Motor innervation to all intrinsic laryngeal muscles except cricothyroid (which is external branch of the superior laryngeal nerve)
RLN injury
Can occur with intubation, neck surgery (thyroid, cervical spine) & positioning injuries (stretching of neck)
If unilaterally injured: VC will be abducted to assume midline position causing stridor and hoarseness.
If bilaterally paralyzed: VCs will be abducted to close to the midline, causing obstruction & aphonia. Aspiration risk, and can be airway emergency.
Parathyroid gland pathophys: labs to obtain pre-op
Serum Ca++, Phos, Mag
neural integrity monitor (NIM) electromyogram (EMG) tracheal tube
- this unique tracheal tube must be positioned so that its color-coded (blue) contact band is appropriately placed between the vocal cords
- nerve monitoring system alerts you with visual and audible tones identify nerves and verify integrity of the nerves during surgery
- utilized, for the head and neck procedures, when laryngeal nerves (LNs) could be injured during the process of surgical dissection. It is particularly useful for identifying the recurrent LN
Thyroid Hormones
thyroxine (T4), triiodothyronine (T3), & calcitonin
- Play a major role in normal growth and development
- Play a chief role in cellular energy metabolism
S/S Hypothyroidism
- usually symptoms are often nonspecific.
- fatigue, lethargy, weakness, joint pain, muscle aches, cold intlerance, constipation, change in voice, and weight gain.
- skin is usually dry and the hair brittle.
- bradycardia, low ECG voltage, and symptoms of heart failure
Untreated severe hypothyroidism
may progress to myxedema and include electrolyte disturbance, hypoventilation, hypothermia, and coma.
hyperthyroidism is commonly caused by
Graves disease, an autoimmune condition in which thyrotropin receptor antibodies continuously mimic the effect of thyroid-stimulating hormone (TSH)
S/S hyperthyroidism
signs and symptoms of hyperthyroidism are cardiac, neurologic, and constitutional.
CV
- increased cardiac sensitivity to catecholamines, resulting in hypertension and tachyarrhythmias
- high-output congestive heart failure or angina, in the absence of coronary plaque
CNS
- Tremor, hyperreflexia, and irritability are common.
- Periodic paralysis, characterized by hypokalemia and proximal muscle weakness, may also occur.
- Fever and heat intolerance are common.
GI
-nausea, vomiting, and diarrhea as well as hepatic dysfunction and jaundice.
a life-threatening severe form of hyperthyroidism
Thyroid storm
- S/S
- Hyperpyrexia (+/- 41 degrees C), cardiac dysfunction, tachycardia, arrhythmias, myocardial ischemia, weakness, delirium & altered mental status, hyperglycemia, hypercalcemia, hyperbilirubinemia, seizures, coma
Outer cortex of adrenal medulla secretes three major classes of steriods:
mineralocorticoids, glucocorticoids, and androgens
the 2 important ones are cortisol (glucocorticoid) and aldosterone (mineralocorticoid)
hypothalamic-pituitary-adrenal (HPA) axis overview
- a major neuroendocrine pathway relevant to the stress response
- chronic administration of corticosteroids suppresses CRH and leads to atrophy of HPA
- in those patients, stressful events during the perioperative period might evoke life-threatening hypotension
- therefore, it is common to administer exogenous corticosteroids (based on the magnitude of stress) to patients considered at risk for suppression of HPA axis
Addison disease
Glucocorticoid deficiency / Hypoaldosteronism
Cushing Syndrome
Glucocorticoid excess
Corticosteroid therapeutic uses:
Reactive airway disease
- Asthma, COPD - Inflammatory conditions
- Inhaled glucocorticoids agents of choice
- Reduce symptoms, improves quality of life, decreases exacerbations
Neuro Critical Care
- Dexamethasone has clinical applications in patients with tumors, bacterial meningitis and prevention or tx of cerebral edema
- Tumors- Initiated to reduce vasogenic edema.
Other uses: N/V prophylaxis, immunosuppression, tx of inflammatory conditions, airway edema, allergic reactions
Catecholamines are produced in what part of the adrenal gland?
adrenal medulla
Synthesis of catecholamines
Tyrosine ⇒ L-DOPA (L-3,4-dihydroxyphenylalanine) ⇒ dopamine ⇒ norepinephrine ⇒ epinephrine.
catecholamine reuptake and degradation
- Undergo reuptake at extraneuronal sites
- Degradation by Catechol-o-methyltransferase (COMT) or monoamine oxidase (MAO).
- This degradation takes place mostly in liver
- Produces the metabolite Vanillylmandelic acid (VMA)
- VMA is excreted in the urine and can be measured to assess cumulative catecholamine secretion!
Pheochromocytoma
Tumor within the adrenal medulla that secretes catecholamines (NE, Epi, and less frequency dopamine)
Intraoperative management of Pheo
- control HTN prior to surgery, preoperative alpha-blockade to prevent intraoperative hypertensive crisis
- surgical stimulation, laryngoscopy may cause exaggerated hemodynamic swings
- infusions of vasoactive should be available, avoiding drugs that cause catecholamine or histamine release
- once tumor is out prepare for hypotension and have pressors available
DKA
Diabetic Ketoacidosis
- precipitated by a lack of insulin in DM type 1
- An acute life-threatening metabolic derangement characterized by increased blood glucose and ketone body formation along with w/ anion gap metabolic acidosis.
HHS
Hyperglycemic Hyperosmolar State
- DM type II
- hyperosmolar condition triggered by a hyperglycemic event
- leads to lactic acidosis, severe hyperglycemia, glucosuria
Sulfonylurea examples:
glipizide, glyburide, glimepiride
Sulfonylurea MOA
- increase insulin release from the beta cells in the pancreas (require functioning beta cells)
- decrease the hepatic clearance of insulin in the liver
Biguanides (Metformin) MOA
-decreases serum glucose by decreasing gluconeogenesis (glucose production in the liver) & it also has an insulin-sensitizing effect and increases peripheral tissue insulin sensitivity and uptake
Thiazolidinediones examples:
rosiglitazone, pioglitazone
Thiazolidinediones MOA
- decrease hepatic glucose production, nd incease inulin sensitivity of adipose tissue, skeletal muscle, and the liver.
- By reducing circulating fat concentrations, they as a result, increase the dependence of the body on carbohydrates/glucose use
Rapid-acting insulin:
- aspart (novalog)
- lispro (humalog)
- glulisine (apidra)
- regular (humulin R, Novolin R)
Intermediate-acting insulin:
NPH
Long-Acting insulin:
- detemir (levemir)
- glargine (lantus)
- glargine (toujeo)
Somatostatin analog examples:
Octreotide and Lanreotide
Somatostatin analog MOA
-Act as INHIBITORS of the release of TSH and Growth Hormone (GH) from the pituitary, of insulin and glucagon from pancreas, and vasoactive peptides from the GI tract.
- Clinical Application
- Somatostatin analogs are used in the perioperative period to block hormone release in neuroendocrine tumors.
- Most often given IV as a continuous infusion in hospital. Can be given SQ.
-Can also be given in 50-100 mcg boluses in response to hemodynamic instability related to vasoactive mediators (carcinoid crisis)
