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TEST TAKING TIPS

Test Taking Tips

  1. Aldosterone and related electrolyte and acid-base imbalances in adrenal disease are popular testing topics.

  2. The MEN syndromes are also a favorite topic. Know these well and understand when to operate and what operation to perform!

THYROID

EMBRYOLOGY, ANATOMY, AND PHYSIOLOGY

What embryologic structures does the thyroid originate from?

  • The medial thyroid comes from the first and second pharyngeal pouches

  • Lateral portions of the thyroid and parafollicular C cells arise from the fourth and fifth pharyngeal pouches

FIGURE 12-1.

Anatomy of the thyroid gland and surrounding structures, viewed anteriorly. a., artery; n., nerve; v., vein. (Reproduced from Brunicardi FC, Andersen DK, Billiar TR, et al. Schwartz's Principles of Surgery. 9th ed. http://www.accessmedicine.com. Copyright © The McGraw-Hill Companies, Inc. All rights reserved.)

What is the arterial supply of the thyroid?

  • Superior thyroid artery (from external carotid artery)

  • Inferior thyroid artery (from thyrocervical trunk)

What is the venous drainage of the thyroid?

  • Superior and middle thyroid veins (drain into internal jugular vein)

  • Inferior thyroid veins (drain into innominate and brachiocephalic veins)

The recurrent laryngeal nerve innervates all of the muscles of the larynx except this muscle?

  • Cricothyroid muscle, which is innervated by the external branch of the superior laryngeal nerve

What structures do the recurrent laryngeal nerves wrap around?

  • Subclavian artery on the right

  • Arch of the aorta on the left

Injury to which nerve results in loss of projection and voice fatigability?

  • Superior laryngeal nerve

DRUGS

What is the mechanism of action of propylthiouracil (PTU) and methimazole?

  • Both drugs block peroxidase oxidation of iodide to iodine, thereby inhibiting incorporation of iodine into T4 and T3

  • PTU also inhibits peripheral conversion of T4 to T3

Which drug crosses the placenta: PTU or methimazole?

  • Methimazole

  • PTU is the safer choice in pregnancy

When steroids are given in severe or acute hyperthyroid conditions? How do they work?

  • Steroids inhibit peripheral conversion of T4 to T3 and lower serum TSH by suppressing the pituitary-thyroid axis

What is the Wolff-Chaikoff effect?

  • Large doses of iodine given after an antithyroid medication can inhibit thyroid hormone release by disrupting the coupling of iodide

  • This is a transient effect

HYPERTHYROIDISM/HYPOTHYROIDISM, AND GOITERS

What is the most common cause of hyperthyroidism?

  • Graves disease, also known as diffuse toxic goiter, is the cause of 60% to 80% of hyperthyroidism

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