Endocrine Pearls (Thyroid, Pituitary, Adrenals)

Question 1

What is the number one cause of Hyperthyroidism?

Answer 1

Multinodular goiter (Grave’s disease)

Question 2

How does PTU work?

Answer 2

decreases hormone synthesis, it also decreases peripheral conversion of T4 to T3. Takes several weeks

Question 3

How does methimazole work?

Answer 3

It also decreases thyroid hormone synthesis, but does NOT have the added benefit of decreasing conversion .

Question 4

Anesthetic concerns for hyperthyroid patients;

Answer 4

d/t potential preoperative morbidity assoc with thyroid storm, patients should be made euthyroid before proceeding with elective cases

Question 5

Ddx for stridor:

Answer 5

hematoma, b/l recurrent laryngeal nerve injury, and laryngospasm due to hypocalcemia

Question 6

What does the RLN supply: B/l vs unilateral RLN injury

Answer 6

motor innervation to all the intrinsic muscles of the larynx EXCEPT the cricothyroid (superior laryngeal nerve) .
RLN injury allows for unopposed action of cricothyroid muscles (vocal cord tensors) causing airway obstruction. Unilateral injury usually results in hoarseness.

Question 7

Which nerve innervates the cricothyroid?

Answer 7

Superior laryngeal nerve

Question 8

How can you determine whether hypocalcemia is the cause of stridor? If it is, what can you do to fix it?

Answer 8

Ca2+ could be drawn, but hypocalcemia is rare before 12 hours post op. Paresthesias, cramps, and facial nerve excitability (Chvostek’s sign). You can give calcium chloride

Question 9

Signs of hyperthyroidism:

Answer 9

tachycardia, weight loss, diarrhea, atrial fib

Question 10

What can precipitate thyroid storm, and when does it happen (usually)

Answer 10

Precipitated by stress, infection, or surgery. Usually happens post op. Use propranolol in emergencies

Question 11

Intraop in hyperthyroidism:

Answer 11

Try to avoid sympathomimetics

Question 12

What does PTH do?

Answer 12

bone resorption, renal distal tubular resorption (also absorbs Mg2+, excretes HCO3-, PO4-), synthesizes 1,25 Dihydroxyvitamin d

Question 13

How does calcium exist? If serum proteins, phosphate, and acidosis increase, what happens to calcium?

Answer 13

50% of serum calcium is ionized, 40% is bound to protein (mainly albumin), 10% to anions.
If those things happen, ionized calcium will decrease. Acidosis decreases protein binding, so more of it becomes free (so free calcium increases with acidosis), but acidosis decreases the calcium that is ionized. Got it.

Question 14

Low phosphate can cause:

Answer 14

hemolysis, platelet dysfunction and impaired myocardial contractility leading to CHF

Question 15

The deeper you go, the sweeter it gets. Explain the Adrenal cortex:

Answer 15

Mineralocorticioids
Glucocrticoids
Androgens

Question 16

Aldosterone is a ______. What does it do? What stimulates it to be released?

Answer 16

It is a mineralocorticoid, and it causes resorption of Na+ (with H20), and secretion of K+ at the distal conv tubule. It is released by stimulation from angiotensin, hyperkalemia, and ACTH.

Question 17

Go over the RAAS

Answer 17

Renin (released by hypotension, sympathetic, or hypokalemia), converts angiotensinogen into AI which is converted to AII (in the lungs), which stimulates aldosterone production.

Question 18

Stress dose steroids-What’s your take?

Answer 18

Anyone receiving 30 mg/day of cortisol (approx equal to 5 mg prednisone) for several weeks in past year could have caused adrenal suppression-You could give stress dose depending on the type of surgery, but I have a low threshold for giving a patient some given any hemodynamic instability
Minor (hernia repair) 25 mg
Moderate: total joint: 50-75
Major: 100-150

Question 19

Bromocriptine: What is it used for? Which receptor does it working on?
What GI issues can it cause?

Answer 19

Bromocriptine is used to treat the excessive excretion of both
prolactin and growth hormone from functional pituitary tumors. It is a synthetic
dopamine-2 receptor agonist that inhibits the secretion of both growth hormone and
prolactin.
It can cause gastroparesis

Question 20

What is the most common pituitary tumor, and what kind of symptoms would they have? What about the other hormones and their tumors?

Answer 20

The
most common functional pituitary adenoma is a prolactinoma, which is associated
with amenorrhea, galactorrhea, and infertility. Other pituitary adenomas secrete
excessive amounts of ACTH, leading to Cushing’s disease (truncal obesity,
abdominal striae, hypertension, and hyperglycemia); growth hormone, leading to
acromegaly (HTN, insulin resistance, visceromegaly, osteoporosis, skeletal
overgrowth, and soft-tissue overgrowth); and TSH, leading to hyperthyroidism (this is
rare).

Question 21

What is the point/function of the pituitary gland?

Answer 21

The anterior pituitary is responsible for the synthesis, storage, and
secretion of the six following tropic hormones: 1) adrenocorticotrophic hormone.
(ACTH), which stimulates the adrenal cortex secretion; 2) prolactin, which stimulates
the secretion of breast milk and inhibits ovulation; 3) human growth hormone, responsible for body growth; 4) thyroid-stimulating hormone (TSH), which stimulates
thyroid secretion and growth; 5) follicle-stimulating hormone (FSH), responsible for
ovarian follicle growth in females and spermatogenesis in males; and 6) luteinizing
hormone, which stimulates ovulation in females and testosterone secretion in males.

Question 22

Posterior pituitary: What’s its purpose?

Answer 22

The posterior pituitary stores and secretes two hormones that are initially synthesized
in the hypothalamus and transported to the posterior pituitary. These two hormones
are (1) antidiuretic hormone (ADH), which promotes water retention and regulates
plasma osmolarity, and (2) oxytocin, which causes uterine contraction and the
ejection of breast milk.

Question 23

What are you thinking if a patient is on octreotide? How does it work?

Answer 23

prolactinoma, I suspect that he is receiving
these medications to treat acromegaly. Octreotide is a somatostatin analogue that
inhibits the release of growth hormone and may actually shrink the size of pituitary
tumors.

Question 24

How is the diagnosis of acromegaly made?

Tests that can be performed?

Answer 24

It’s based on clinical suspicion: due to the presence of several characteristic manifestations, and confirmed by
biochemical testing. The characteristic manifestations of acromegaly include skeletal
overgrowth (large body, hands, and feet; prognathism), soft tissue overgrowth (large
lips, tongue, epiglottis, and vocal cords), recurrent laryngeal nerve paralysis
(secondary to stretching caused by overgrowth of surrounding structures), peripheral
neuropathy (secondary to trapping caused by the overgrowth of surrounding tissue),
visceromegaly, glucose intolerance, osteoarthritis, osteoporosis, hyperhidrosis, and
skeletal muscle weakness.

Tests: measurement of serum IGF-I (the most reliable test since it is less variable throughout
the day), measurement of serum growth hormone (varies from hour-to-hour with
exercise, sleep, and food ingestion),

Question 25

What are your anesthetic concerns in a patient with acromegaly?

Answer 25

Difficult intubation due to changes in soft tissue and skeletal structure