Apex Endocrine Flashcards
compare and contrast the architecture of the nervous system and endocrine system.
nervous system = wired
- electrochemical
- neurotransmitters
- synapse
- specific cell target
- fast speed
- short duration
endocrine system = wireless
- travels in blood
- hormones
- endocrine, paracrine, autocrine
- more widespread target
- slow speed
- long duration
compare and contrast positive and negative feedback loops in the endocrine system.
negative feedback: hormone reduces it’s own release via short or long loops
positive feedback: hormone increases it’s own release
pathway: hypothalamus anterior pituitary endocrine gland hormone target tissue
compare and contrast how the hypothalamus communicates w/ anterior and posterior pituitary glands.
posterior pituitary via neural connections
- ADH produced by supraoptic nuclei
- oxytocin produced in paraventricular nuclei
- carried by axonal transport along the pituitary stalk
anterior pituitary via releasing and inhibiting hormones
- released into the hypophyseal portal vessels
- transported along the pituitary stalk to influence hormone secretion by anterior pituitary gland
name the 7 hypothalamic hormones, and identify their effects on the anterior pituitary gland
luteinizing hormone releasing hormone
- increased FSH
- icnreased LH
corticotropin releasing hormone
- increased ACTH
thyrotropin releasing hormone
- increased TSH
prolactin releasing factor and prolactin inhibiting factor
- prolactin
growth hormone releasing hormone and inhibiting hormone
- GH
where is the pituitary gland located? what is another name for the anterior and posterior pituitary glands?
in the sella turcica, and it is connected to the hypothalamus by the pituitary stalk.
anterior = adenohypophysis posterior = neurohypophysis
what hormones are released from the anterior pituitary gland?
"FLAT PIG" FSH LH ACTH TSH Prolactin GH
what is the function of each anterior pituitary hormone?
FSH: germ cell maturation and ovarian follicle growth (females)
LH: testosterone production (males) and ovulation (females)
ACTH: adrenal hormone release
TSH: thyroid hormone release
prolactin: lactation
GH: cell growth
what hormones are released from the posterior pituitary gland? What are their functions?
ADH: water retention
oxytocin: uterine contraction and breast feeding
compare and contrast the presentation and treatment of SIADH and DI.
SIADH: too much ADH
- d/t TBI, CA, lung dz, carbamazepine
- presents as hyponatremia w/ hypotonic osm
- can be euvolemic or hypervolemic
- low UOP w/ high urine osm, Na+
- tx: fluid restriction +/- hypertonic saline, demeclocycline
DI: too little ADH
- d/t pit surgery, TBI, SAH
- presents as polyuria w/ low urine osm, Na+
- can be hypovolemic or euvolemic, w/ high serum osm and Na+
- tx: DDAVP, supportive
what are the anesthetic implications of acromegaly?
- distorted facial features = difficult mask
- large tongue, teeth, epiglottis = difficult DL
- subglottic narrowing + VC enlargement = use a smaller tube
- turbinate enlargement = epistaxis risk, avoid nasal ETT
- OSA is common
- increased risk of HTN, CAD, dysrhythmias
- glucose intolerance
- skeletal m weakness
- entrapment neuropathies are common
compare and contrast T4 and T3
T4
- directly released from thyroid
- highest concentration in the blood (think of it as a delivery vehicle)
- high PB, low potency
- t1/2 7 days
T3
- some released from thyroid, but most is extrathyroid T4 conversion
- highest concentration at the target cell (think of it as active form)
- less PB, high potency
- t1/2 1 day
how does iodine deficiency affect T3 and T4
TSH stimulates the iodide pump. Iodine is a substrate that the thyroid requires to synthesize T3 and T4. When iodine isn’t readily available, the thyroid is unable to produce a sufficient quantity
how does thyroid hormone affect cardiac function?
increases myocardial performance independent of the ANS:
- increased chronotropy
- increased inotropy
- increased lusitropy
- decreased SVR
effects on the ANS that impact cardiac function
- increase # and sensitivity of cardiac B receptors
- decrease # of cardiac muscarinic receptors
how does thyroid hormone affect the respiratory system?
increased BMR –> increased O2 consumption –> increased CO2 production –> increased MV (Vt and RR)
how does thyroid hormone affect MAC?
it doesn’t affect the brain, and by extension, hyper/hypothyroidism don’t affect MAC.
They do however, affect the speed of anesthetic induction when IA is used:
- hyper = slower induction d/t higher CO
- hypo = faster induction d/t lower CO
what is the most common etiology of hyperthyroidism? What are the other causes?
most common: graves (autoimmune)
others:
- myasthenia gravis
- multinodular goiter
- carcinoma
- pregnancy
- pituitary adenoma
- amiodarone
what is the most common etiology of hypothyroidism? What are the other causes?
most common: Hashimoto’s (autoimmune)
others:
- iodine deficiency
- hypothalamic-pituitary dysfunction
- neck radiation
- thyroidectomy
how are TSH, T3, and T4 levels affected by hyper and hypothyroidism?
hyperthyroidism: low TSH + high T3 and T4
hypothyroidism: high TSH + low T3 and T4
what is the difference b/n myxedema coma and cretisim?
myxedema coma occurs w/ end stage hypothyroidism. coma is a consequence (not a cause) of severely impared thyroid function
cretinism is caused by neonatal hypothyroidism that leads to physical and mental retardation
list 3 thionamides that can be used to treat hyperthyroidism. What is their mechanism of action?
thionamides: propylthiouracil (PTU), methimazole, carbimazole
inhibit thyroid synthesis by blocking iodine addition to the tyrosine residues on thyroglobulin. PTU also inhibits the peripheral conversion of T4 to T3
- require 6-7 weeks to achieve a euthyroid state
- only available PO, but can be crushed and given via OGT
why are beta blockers used to treat hyperthyroidism?
reduce SNS stimulation and inhibit peripheral conversion of T4 to T3
what are contraindications to radioactive iodine?
pregnancy
breast feeding
when is it ok for a patient w/ hyperthyroidism to undergo surgery? how about the hypothyroid patient?
hyper:
- do not proceed to elective surgery until pt is euthyroid.
- emergency surgery warrants administration of BB, potassium iodide, glucocorticoid, and PTU
hypo: ok to proceed if mild to moderate disease
what is the best way to secure the airway in a patient w/ a large goiter?
on boards, goiter = awake intubation
the next best response is a technique that maintains spontaneous ventilation
which anesthetic agents should be avoided in the hyperthyroid patient?
sympathomimetics
anticholinergics
ketamine
pancuronium
describe the presentation of thyroid storm
medical emergency that can occur in hyperthyroid and euthyroid patients
- generally brought on by stressful events (infection, surgery, etc.)
- most commonly occurs 6-18hrs after surgery
s/s
- fever >38.5C
- tachycardia/arrhythmias
- HTN
- CHF
- shock
- confusion and agitation
- N/V
under anesthesia, thyroid storm can mimic:
- MH
- pheo
- neuroleptic malignant syndrome
- light anesthesia
how do you manage the patient w/ thyroid storm?
- cardiopulmonary support
- active cooling measures
- PTU, methimazole
- BB
- tx fever w/ tylenol
- avoid aspirin (it can dislodge T4 from plasma proteins and increase unbound fraction)
- management is the same in pregnant and nonpregnant pts
discuss recurrent laryngeal nerve injury in the context of thyroidectomy.
RLN innervates all the intrinsic muscles except cricothyroid. Injury can cause upper airway obstruction
- unilateral = hoarseness
- bilateral = a/w obstruction
- phonate “E” or “moon” to assess for nerve injury
- NIMS tube provides ability to assess for nerve injury intraoperatively
- at end of procedure DL can be used to assess VC function as well as glottic edema.
why is hypocalcemia a potential complication of thyroidectomy? How and when does it present?
resection of parathyroid glands w/out reimplantation –> hypocalcemia at least 6-12hrs post-op.
s/s (d/t increased nerve and muscle irritability):
- m spasm –> tetany
- laryngospasm
- MS changes
- hypotension
- prolonged QT
- paresthesias
- Chvosteks (jaw) and Trousseau’s (forearm)
how does hypothyroidism affect gastric emptying?
delays it
–> increased risk of aspiration
what are the 3 zones of the adrenal cortex? What substance does each synthesize?
outside to inside: “GFR releases salt, sugar, sex”
outermost: zona glomerulosa releases mineralocorticoids (aldosterone)
middle: zona fasciculata releases glucocorticoids (cortisol)
innermost: zona reticularis releases androgens (DHEA)
describe the steps involved in the RAAS.
- decreased renal perfusion, SNS activation (B1), and/or tubuloglomerular feedback
- increased renin released from juxtaglomerular cells
renin: angiotensinogen –> angI
ACE: ang1 –> ang2
- vasoconstriction
ang2 = increased aldosterone
- increased Na+, H2O reabsorption
- increased K+, H+ excretion
how much cortisol is produced per day? what is the normal cortisol level?
15-30mg/day
normal serum level 12mcg/dL
stress can increase cortisol production upwards of 100mg/day, w/ serum level 30-50mcg/dL during and after major surgery
how does cortisol affect cardiovascular function?
improves myocardial performance by increasing the number and sensitivity of B receptors on the myocardium
cortisol is also required for the vasculature to respond to the vasoconstrictive effects of catechols.
