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50 Cards in this Set

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THYROID: AM
THYROID: AM
What element is necessary for synthesis of thyroid hormones
iodine
What is the most active thyroid hormone and has 3 molecules of iodine attached
T3
How is dietary iodine absorbed
follicle cells in the thyroid
What is necessary to actively metabolize with T4 to form T3
iodine
Describe the role of TRH (thyrotropin releasing hormone) in regulating thyroid hormones levels
TRH is secreted by hypothalamus and contributes to regulating TSH
Describe the role of TSH (thyroid stimulating hormone) in regulating thyroid hormone levels
TSH is secreted by the anterior pituitary and regulates the synthesis of T3 and T4
What are the 2 major thyroid hormones
T4, T3
What hormone constitues 90% of secretory production of thyroid gland and is most abundant thyroid hormone in serum
T4
What hormone constitutes 90% of circulating and most active thyroid hormone and is derived from deiodination of T4 in peripheral tissues, primarily the liver
T3
What is the role of TSH in evaluating thyroid disease
best initial test to determine biochemical thyroid status in healthy pts
What is the role of total T4 in evaluating thyroid disease
measured bound and free hormone in serum
What is the role of T4 or T3 resin uptake in evaluating thyroid disease
estimate of the serum protein binding sites
What is the role of thyroid hormone bindking ratios (THBR) in evaluating thyroid disease
estimate of the serum protein binding sites
What is the role of Free T4 Index (FTI) in evaluating thyroid disease
Estimate of free T4 concentrations
What is the role of Free T4 equilibrium dialysis method in evaluating thyroid disease
gold standard for measurement of free T4 concentrations, expensive, time consuming to measure
What is the role of Free T4 analog method in evaluating thyroid disease
Direct measurement of free T4 concentrations, may not be more reliable than FTI
What is the role of Total T3 in evaluating thyroid disease
Second-line test, measures bound and free hormone in serum
What is the role of Free T3 analog method in evaluating thyroid disease
No advantage over total T3
What is the role of Reverse T3 in evaluating thyroid disease
Inactive T4 metabolite, rarely clinically indicated
What is the role of Thyroid antibodies (anti-Tg, anti-TPO)in evaluating thyroid disease
Second-line test, determines presence of autoimmune thyroid disease
What is the role of Thyroglobulin in evaluating thyroid disease
Second-line test, intrinsic thyroid protein, useful as a marker for differentiated thyroid cancer
Describe the most common causes of hypothyroidism in the USA as opposed to the most common cause worldwide
World: iodine deficiency. USA: autoimmune; failure of thyroid to produce sufficient thyroid hormone
What is the most common cause of hypothyroidism
AKA primary: failure of thyroid to produce sufficient thyroid hormone
Describe the typical presentations of Hashimoto's thyroiditis and how it affects thyroid function
autoimmune, leading cause of goiter in US. impairs thyroxine synthesis and increases hormone into circulation and can lead to hypothyroidism due to fnx loss of thyroid
What is the most common cause of thyroiditis
Hashimoto's
Define cretinism
Thyroid hormone defiency at birth causing physical & mental development, myxedema, dystrophy of bones & soft tissues, lowered basal metabolism.
Describe typical signs and symptoms of hypothyroidism and clinical picture of severe hypothyroidism with myxedema
1)hypothermia 2)resp depression 3)unconsciousness. Other features include bradycardia, macroglossia, delayed reflexes, dry, rough skin. Dilutional hyponatremia common ↑ CPK, ↑ LDH, acidosis, and anemia common findings
Describe symptoms and PE of hypothyroidism
weakness, fatigue, cold intolerance, constipation, menorrhagia, hoarseness, dry, puufy skin, bradycardia, brittle hair, slow tendon reflex relaxation, cognitive dullness
Describe symptoms and PE of hyperthyroidism
nervousness, sweating, heat intolerance, palpitations, easy fatigue, dyspnea, weakness, weight loss despite ↑ appetite, loose stools, tachycardia, goiter, tremor, thyroid bruit, a-fib, eye signs
Describe the drug of choice for treating hypothyroidism
Levothyroxine starting dose depending on age, height, weight, presence of chronic disease and severity and duration of sx
Describe drug treatment in elderly patients with cardiac history in treating hypothyroidism
caution, start low and go slow.
What is the most common form of hyperthyroidism
Graves disease
Discuss symptoms of Graves disease
diffuse enlarged thyroid, hyperactivity of gland, presence of antibodies, more common in women
Discuss pituitary in its involvment with hyperthyroidism
TSH hypersecretion by pituitary may be caused by a tumor
How can pregnancy affect thyroid
very high serum levels of hCG (like with trophoblastic tumor) may cause sufficient receptor activation of TSH receptors and cause thyrotoxicosis (hyperthyroidism)
Briefly describe the pros and cons of treating hyperthyroidism with antithyroid drugs (propylthiouracil and methimazole)
Pros: requires less frequent dosing, lower risk of liver problems Cons: serum sickness, loss tast, alopecia, nephrotic syndrome, hypoglycemia
Briefly describe the pros and cons of treating hyperthyroidism with radioactive iodine
Pros: destroys overactive thyroid tissue (diffuse or nodular)no risk of subsequent thyroid CA Cons: fetal radition harmful, graves opthalmopathy worsens 15%, high incidence of hypothyroidism
Briefly describe the pros and cons of treating hyperthyroidism with surgery
Pros: prefered for pregnancy, pt's with large goiters, significant chance of malignancy. Cons: morbidity possible if damage to laryngeal nerve, vocal cord paralysis, hypothyroidism
Describe syndrome of toxic mulitnodular goiter
similar to graves except no infiltrative ophthalmopathy, scan shows patchy distribution, no medical remission. Treat with radioiodine after antithyroid drug pretreatment
Describe syndrome of subacute thyroiditis
probably viral. Px tender gland. maybe thryotoxic early with later hypothyroid phase. Tx: NSAIDS, ASA, b-blockers. Resolves spontaneously in weeks to months.
Describe workup for a patient with a solitary thyroid nodule
Differentiate carcinoma from benign causes: solitary hard nodule irregular or fixed suggests malignancy. Fine needle aspiration, radionuclide scanning, ultrasound and ancillary lab tests.
Describe what hot nodules on radioisotope scanning would indicate
shows radionuclide uptake in region of palpable nodule indicating that it is functioning
Describe what cold nodules on radioisotope scaning would indicate
shows decreased radionuclide uptake of palpable nodule indicating it itsn't functioning
What is the clinical significance of hot or cold nodules on radioisotope scanning
typical malignant nodule is "cold." Incidence of malignancy in "hot" nodule <1%.
What are some causes for thyroid nodulesand cancer
colloid nodule, thyroid cyst, thyroid adenoma, thyroiditis
What is the most common type of thyroid nodule
colloid nodule
Name the 4 types of thyroid cancer
Papillary (most common), follicular, anaplastic, medullary
Name 3 types of thyroiditis
Hashimotos (most common) subacute thyroiditis, postpartum thyroiditis
Name the 2 causes of hypothyroidism
Primary (autoimmune) and rarely pituitary insufficiency