Thyroid Disease

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Thyroid Disease

  1. 1. Thyroid Disease Intern Conference
  2. 2. Normal Physiology <ul><li>TSH stimulates secretion of T4 and T3 from thyroid </li></ul><ul><li>Most serum T3 produced by deiodination of T4 </li></ul><ul><li>Think of T3 as active hormone and T4 as prohormone </li></ul><ul><li>Only small fraction total T4 and total T3 is unbound – therefore free and active </li></ul>http://agrc.ucsf.edu/supplements/endocrine/15_hpt_axis.html
  3. 3. TFTs <ul><li>TSH is the screening test of choice for thyroid function (nml 0.3-5mU/L) </li></ul><ul><li>Unbound, free portion of T4 is indicative of thyroid status </li></ul><ul><li>Previously, estimate of FT4 was determined by means of T3 resin uptake (total T4 x T3RU ~ free thyroxine level) </li></ul><ul><li>Free T4 assay is currently preferred </li></ul>
  4. 4. Screening <ul><li>Screening at periodic health exam without signs/symptoms is controversial </li></ul><ul><li>Universal screening is recommended for thyroid dysfxn in pregnant women or those hoping to become pregnant </li></ul>
  5. 5. Diagnostic Approach TSH low Free T4 high 1 o Hyperthyroid Subclinical Hyperthyroid nml low 2 o Hypothyroid nml ? Secondary (central) dz high Free T4 high 2 o Hyperthyroid Or Thyroid hormone resistance nml Subclinical Hypothyroid low 1 o Hypothyroid RAIU diffuse homogeneous heterogeneous Grave’s Dz Toxic multinodular goiter focal Functioning Adenoma None Serum Thyroglobulin low Thyrotoxicosis factitia Iodine load high Thyroiditis Struma ovarii
  6. 6. Hypothyroidism <ul><li>Slowing of metabolic processes </li></ul><ul><ul><li>Sxs: Fatigue, weakness, cold intolerance, weight gain, cognitive dysfunction, mental retardation, constipation, growth failure </li></ul></ul><ul><ul><li>Signs: Slow movement, slow speech, delayed relaxation of tendon reflexes, bradycardia </li></ul></ul><ul><li>Accumulation of matrix substances </li></ul><ul><ul><li>Sxs: Dry skin, hoarseness, edema </li></ul></ul><ul><ul><li>Signs: Periorbital edema, puffy facies, loss of eyebrows, coarse skin, macroglossia </li></ul></ul><ul><li>Other </li></ul><ul><ul><li>Sxs: Decreased hearing, myalgia and paresthesia, depression, menorrhagia, pubertal delay </li></ul></ul><ul><ul><li>Signs: Diastolic HTN, pleural and pericardial effusions, ascites, galactorrhea, hyperlipidemia, atherosclerosis </li></ul></ul>
  7. 7. Hypothyroidism—etiologies <ul><li>Primary (90%) </li></ul><ul><ul><li>Hashimoto’s thyroiditis </li></ul></ul><ul><ul><ul><li>May be part of polyglandular autoimmune syndrome (Addison’s, DM), incr’d incidence of Sjogren’s </li></ul></ul></ul><ul><ul><ul><li>+Antithyroid peroxidase (anti-TPO) abs in >90% </li></ul></ul></ul><ul><ul><li>Recovery after thyroiditis </li></ul></ul><ul><ul><li>Iodine deficiency </li></ul></ul><ul><ul><li>Surgical destruction, s/p radioactive iodine </li></ul></ul><ul><ul><li>Amiodarone, lithium </li></ul></ul><ul><li>Secondary </li></ul><ul><ul><li>Hypothalamic or pituitary failure </li></ul></ul>
  8. 8. Hypothyroidism—treatment <ul><li>Overt </li></ul><ul><ul><li>Levothyroxine (1.5-1.7 µ g/kg/day), recheck TSH q5-6wks and titrate until euthyroid </li></ul></ul><ul><ul><li>Lower starting dose if at risk for ischemic heart disease (0.3-0.5 µ g/kg/d) </li></ul></ul><ul><li>Subclinical </li></ul><ul><ul><li>Rx controversial </li></ul></ul><ul><ul><ul><li>Follow expectantly or treat to improve mild sx </li></ul></ul></ul><ul><ul><ul><li>Most initiate Rx if TSH>10mU/L, goiter, pregnancy or infertility </li></ul></ul></ul><ul><ul><ul><li>Keep in mind risk of A. fib and accelerating osteoporosis with treatment </li></ul></ul></ul>
  9. 9. Hyperthyroidism <ul><li>Sympathetic overactivity </li></ul><ul><ul><li>Restlessness, sweating, tremor, moist warm skin, fine hair, tachycardia (A. fib), weight loss, increased stool frequency, menstrual irregularities, hyperreflexia, osteoporosis, lid lag </li></ul></ul>
  10. 10. Hyperthyroidism—etiologies <ul><li>Graves Disease </li></ul><ul><ul><li>+ thyroid antibodies </li></ul></ul><ul><ul><ul><li>TSI, ANA </li></ul></ul></ul><ul><ul><li>Classic manifestations </li></ul></ul><ul><ul><ul><li>Goiter: diffuse, nontender, w/ thyroid bruit </li></ul></ul></ul><ul><ul><ul><li>Ophthalmopathy: periorbital edema, proptosis, diplopia </li></ul></ul></ul><ul><ul><ul><li>Pretibial myxedema </li></ul></ul></ul>http://www.elp.manchester.ac.uk/pub_projects/2002/MNBY9APB/THETHYrOIDCLINICAL.htm
  11. 11. Hyperthyroidism—etiologies <ul><li>Thyroiditis </li></ul><ul><ul><li>Thyrotoxic phase of subacute thyroiditis </li></ul></ul><ul><ul><ul><li>Painful = viral, granulomatous, or de Quervain’s (fever, ↑ESR, Rx = NSAIDs, steriods) </li></ul></ul></ul>
  12. 12. Hyperthyroidism—etiologies <ul><li>Others: </li></ul><ul><li>Toxic adenomas (single or multinodular goiter) </li></ul><ul><li>Rare functioning thyroid carcinoma </li></ul><ul><li>TSH-secreting pituitary tumor </li></ul><ul><li>Pituitary resistance to thyroid hormone </li></ul><ul><li>Amiodarone, iodine-induced, thyrotoxicosis factitia, struma ovarii </li></ul>
  13. 13. Hyperthyroidism—uptake <ul><li>A. Normal </li></ul><ul><li>B. Graves’ Dz </li></ul><ul><li>C. Toxic Multinodular Goiter </li></ul><ul><li>D. Toxic Adenoma </li></ul><ul><li>E. Thyroiditis </li></ul>http://embryology.med.unsw.edu.au/Notes/endocrine8.htm
  14. 14. Hyperthyroidism—treatment <ul><li>Beta-blockers: control sxs </li></ul><ul><ul><li>Propranolol decr peripheral T4 -> T3 conversion </li></ul></ul><ul><li>Graves’ Dz </li></ul><ul><ul><li>PTU (safe in pregnancy) or methimazole </li></ul></ul><ul><ul><ul><li>Rare side effect: agranulocytosis </li></ul></ul></ul><ul><ul><li>Radioactive iodine </li></ul></ul><ul><ul><ul><li>75% of treated pts become hypothyroid </li></ul></ul></ul><ul><ul><li>Surgery </li></ul></ul><ul><ul><ul><li>Usually reserved for obstructive goiter </li></ul></ul></ul><ul><li>Toxic Adenoma or TMNG </li></ul><ul><ul><li>RAI or surgery </li></ul></ul>
  15. 15. Sick Euthyroid Syndrome <ul><li>TFT abnormalities in pts w/ severe nonthyroidal illness </li></ul><ul><li>If thyroid dysfunction is suspected in critically ill patients, TSH alone is not reliable – must measure all TFTs </li></ul><ul><li>Replacement thyroxine not helpful or recommended for critically ill unless other s/s of hypothyroidism </li></ul>
  16. 16. Amiodarone and Thyroid Dz <ul><li>Causes both hypothyroidism and hyperthyroidism </li></ul><ul><ul><li>Hypothyroidism </li></ul></ul><ul><ul><ul><li>“ Wolff-Chaikoff” effect: iodine load decreases iodine uptake, organification, and release of T4 & T3 </li></ul></ul></ul><ul><ul><ul><li>Inhibits coversion of T4 -> T3 </li></ul></ul></ul><ul><ul><ul><li>Direct/immune-mediated thyroid destruction </li></ul></ul></ul><ul><ul><li>Hyperthyroidism </li></ul></ul><ul><ul><ul><li>Type 1 = underlying MNG or autonomous thyroid tissue </li></ul></ul></ul><ul><ul><ul><li>Type 2 = destructive thyroiditis </li></ul></ul></ul><ul><ul><ul><ul><li>Increased release of preformed T4 and T3  hyperthyroidism  hypothyroidism  recovery </li></ul></ul></ul></ul>
  17. 17. Thyroid nodules <ul><li>No difference in incidence of thyroid carcinoma between thyroids with single or multiple nodules </li></ul><ul><li>***Perform FNA/biopsy on all “cold or non-specific” thyroid nodules >1.0cm </li></ul>
  18. 18. Thyroid Nodules—types <ul><li>Thyroid adenoma – ablate, resect, or med Rx </li></ul><ul><li>Thyroid Carcinoma </li></ul><ul><ul><li>Parafollicular (medullary) </li></ul></ul><ul><ul><ul><li>Affects parafollicular C cells causing increased serum calcitonin </li></ul></ul></ul><ul><ul><ul><li>15% seen in MEN 2A (+ parathyroid hyperplasia, pheochromocytoma </li></ul></ul></ul><ul><ul><li>Follicular </li></ul></ul><ul><ul><ul><li>Papillary, Follicular, Anaplastic </li></ul></ul></ul>

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