Thyroid II Flashcards
What are important facts about thyroid hormone receptors? ie receptor type, favorite agonist, other facts
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
Metabolic effects of thyroid hormone
- calorigenesis: ultimate catabolic hornome
- protein metab: stimulates protein synthesis and protein balance at low levels but promotes protein degradation at high levels
- Carb metab: low levels use glucose; high levels cause glycogenolysis and gluconeogenesis
- Increase lipolysis and fatty acid oxidation; decrease cholesterol
When do you test thyroid function?
abnormal thyroid gland on physical exam: nodules, diffuse enlargement, or pain
symptoms of hyper or hypothyroidism
screening
screening with some meds
When do you do screening thyroid function tests?
women every 2-3 yrs
men every 4-5 yrs
pregnancy
post-partum
what drugs require monitoring of thyroid function tests?
thyroxine replacement or anti-thyroid drugs
lithium and amiodarone
What are the most useful thyroid function tests? Notes on each
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.
Factors that increase total T4
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
Factors that decrease total T4
anything that decreases thyroid binding globulin:
androgens
glucocorticoids
nephrotic syndrome
difference in information btw a thyroid scan and uptake and thyroid ultrasound
scan and uptake is more of a functional test
ultrasound gives more structural information
When would you absolutely do a thyroid biopsy?
thyroid nodule with normal thyroid levels: biopsy
symptoms of hypothyroidism
fatigue, weakness, cold intolerance, weight gain, constipation, dry skin, edema, cognitive dysfunction, menorrhagia, (myalgia, hoarseness, arthralgia)
Physical exam symptoms of hypothyroidism
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)
Pathophysiology of hypothyroidism
slowing of metabolic activity and build up of matrix substances in the tissues
labs with hypothyroid
high TSH and low FT4 normochromic, normocytic anemia decr. sex hormone binding protein conc hponatremia hyperlipidemia
Causes of primary hyporthyroidism
Hashimoto’s/chronic autoimmune
iatrogenic (radioactive iodide, thyroidectomy
transient: subacute thyroiditis, post-partum
myxedema coma
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
Symptoms of hyperthyroid
anxiety, emotional lability, weakness, tremor, heat intolerance, palpitations, itching, weight loss, incr. sweating, hyperdefecation/diarrhea, irregular or absent menses, gynecomastia
Signs of hyperthyroid
hyperactivity, warm skin, fine thin hair, tachycardia, systolic HTN, tremor, muscle weakness, hyperreflexia, eyelid retraction. look like hypersympathetic
Differential for hyperthyroidism
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
thyroid studies with hyperthyroidism
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
Radioactive scan: differentiation btw causes of hyperthyroid
graves: high uptake and big gland
toxic adenoma: uptake in a discrete nodule
toxic multinodular goiter: patchy uptake everywhere
thyroiditis: low uptake
specific clinical manifestations of Grave’s disease
orbitopathy: protrusion of the eye, redness, pain, and double vision.
dermopathy: rash on leg with infiltrative dermopathy from accumulation of glycosaminoglycans
treatment of hyperthyroid
graves: thionamides or radiiodine
toxic adenoma: radioiodine
toxic multnodular goiter: thinamides or radiodine
thyroiditis: pain meds and time
thyroid storm
life-threatening hyperthyroidism
hyperthermia, arrhythmias, delirium, and seizures
treat with thioanmides,iodine, and beta blockers
