Thyroid II

Question 1

What are important facts about thyroid hormone receptors? ie receptor type, favorite agonist, other facts

Answer 1

nuclear receptor
affinity for T3 10X greater than for T4
many thyroid recepotrs are present in different tissues; mutations in the receptor can cause thyroid hormone resistance

Question 2

Metabolic effects of thyroid hormone

Answer 2

1. calorigenesis: ultimate catabolic hornome
2. protein metab: stimulates protein synthesis and protein balance at low levels but promotes protein degradation at high levels
3. Carb metab: low levels use glucose; high levels cause glycogenolysis and gluconeogenesis
4. Increase lipolysis and fatty acid oxidation; decrease cholesterol

Question 3

When do you test thyroid function?

Answer 3

abnormal thyroid gland on physical exam: nodules, diffuse enlargement, or pain
symptoms of hyper or hypothyroidism
screening
screening with some meds

Question 4

When do you do screening thyroid function tests?

Answer 4

women every 2-3 yrs
men every 4-5 yrs
pregnancy
post-partum

Question 5

what drugs require monitoring of thyroid function tests?

Answer 5

thyroxine replacement or anti-thyroid drugs

lithium and amiodarone

Question 6

What are the most useful thyroid function tests? Notes on each

Answer 6

TSH: most sensitive determination of hormone status in patients with intact pituitary. If this is normal, it suggests you’ve made enough T3 to be euthyroid.
T4: direct measure of free T4.

Question 7

Factors that increase total T4

Answer 7

anything that increases thyroid binding globulin (made by liver)
estrogens, hepatitis. Estrogens mean that you may have to adjust doses in thyroid patients during pregnancy or menopause
Or, amiodarone, which decreases T4 to T3 conversion
psychosis
familial dysalbuminemic hyperthyroxinemia: autosomal dominant disorder whereby albumin binds T4 preferentially

Question 8

Factors that decrease total T4

Answer 8

anything that decreases thyroid binding globulin:
androgens
glucocorticoids
nephrotic syndrome

Question 9

difference in information btw a thyroid scan and uptake and thyroid ultrasound

Answer 9

scan and uptake is more of a functional test

ultrasound gives more structural information

Question 10

When would you absolutely do a thyroid biopsy?

Answer 10

thyroid nodule with normal thyroid levels: biopsy

Question 11

symptoms of hypothyroidism

Answer 11

fatigue, weakness, cold intolerance, weight gain, constipation, dry skin, edema, cognitive dysfunction, menorrhagia, (myalgia, hoarseness, arthralgia)

Question 12

Physical exam symptoms of hypothyroidism

Answer 12

delated deep tendon reflex relaxation
dry skin
bradycardia
puffy face and periobital edema
slow movement and speech
diastolic HTN
galactorrhea
(ascites, pericardial effusion, loss of lateral 1/3 of eyebrows)

Question 13

Pathophysiology of hypothyroidism

Answer 13

slowing of metabolic activity and build up of matrix substances in the tissues

Question 14

labs with hypothyroid

Answer 14

high TSH and low FT4
normochromic, normocytic anemia
decr. sex hormone binding protein conc
hponatremia
hyperlipidemia

Question 15

Causes of primary hyporthyroidism

Answer 15

Hashimoto’s/chronic autoimmune
iatrogenic (radioactive iodide, thyroidectomy
transient: subacute thyroiditis, post-partum

Question 16

myxedema coma

Answer 16

life-threatening hypothyroidism
usually baseline hypothyroidism with aprecipitating event like trauma, infection, MI or drugs
causes severe hypothermia, hypoxia, and decreased cardiac function. requires aggressive thyroid hormone replacement

Question 17

Symptoms of hyperthyroid

Answer 17

anxiety, emotional lability, weakness, tremor, heat intolerance, palpitations, itching, weight loss, incr. sweating, hyperdefecation/diarrhea, irregular or absent menses, gynecomastia

Question 18

Signs of hyperthyroid

Answer 18

hyperactivity, warm skin, fine thin hair, tachycardia, systolic HTN, tremor, muscle weakness, hyperreflexia, eyelid retraction. look like hypersympathetic

Question 19

Differential for hyperthyroidism

Answer 19

Grave’s disease (abx agains the TSH receptor), subacute thyroiditi (esp. if thyroid is tender), early hashimoto’s (esp if non-tender), toxic adenoma, toxic multinodular goiter

Question 20

thyroid studies with hyperthyroidism

Answer 20

low TSH and high FT4
if normal FT4 and high T3 think of T3 toxicosis
high TSH and FT4: consider pituitary tumor
if you find thyroid stimulating immunoglobulin, you have Grave’s disease

Question 21

Radioactive scan: differentiation btw causes of hyperthyroid

Answer 21

graves: high uptake and big gland
toxic adenoma: uptake in a discrete nodule
toxic multinodular goiter: patchy uptake everywhere
thyroiditis: low uptake

Question 22

specific clinical manifestations of Grave’s disease

Answer 22

orbitopathy: protrusion of the eye, redness, pain, and double vision.
dermopathy: rash on leg with infiltrative dermopathy from accumulation of glycosaminoglycans

Question 23

treatment of hyperthyroid

Answer 23

graves: thionamides or radiiodine
toxic adenoma: radioiodine
toxic multnodular goiter: thinamides or radiodine
thyroiditis: pain meds and time

Question 24

thyroid storm

Answer 24

life-threatening hyperthyroidism
hyperthermia, arrhythmias, delirium, and seizures
treat with thioanmides,iodine, and beta blockers