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