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USMLE Step 2 — Lesson 15: Thyroid Disease

THYROID DISEASE

HYPOTHYROIDISM

Clinical features• Signs of metabolic slow-down, ie, lethargy, fatigue, slowness of speech

• Cold intolerance

• Constipation

• Weight gain

HYPOTHYROIDISM

Clinical features• Voice and hair change

• Nonpitting edema, ie, myxedema

• Diminished deep tendon reflexes

• Bradycardia

HYPOTHYROIDISM

Myxedema coma• ntreated se!ere hypothyroidism

• "ay be triggered by acute precipitant, eg, infection• #atients may present with hypothermia, hypoglycemia, shoc$, and

hypo!entilation• %herapy& thyroid and adrenal hormone replacement

HYPOTHYROIDISM

Diagnosis of y!otyroidism• 'ow total %( and %)

• *le!ated %S+

• 'ow radioacti!e iodine upta$e

HYPOTHYROIDISM" Cronic Tyroiditis #Hasimoto$s Tyroiditis%

•  utoimmune disorder usually affecting women

•  ntithyroid antibodies present

• %hyromegaly due to lymphocytic infiltration

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• +ypothyroidism gradually de!elops

HYPOTHYROIDISM" Cronic Tyroiditis #Hasimoto$s Tyroiditis%

Diagnosis•  ntimicrosomal antibodies or antithyroglobulin antibodies

• Suspected in patients with symmetric, usually nontender, nontoxic goiters

• #atients may be euthyroid or hypothyroid• %reat with '-thyroxine to decrease sie of gland and for the hypothyroidism

HYPOTHYROIDISM

Tera!y• %hyroid hormone replacement, ie, synthetic '-thyroxine

• Begin with low doses in older patients and in those with se!erehypothyroidism

HYPERTHYROIDISM

Clinical features• ./!eracti!e. metabolism

• Sweating

• +eat intolerance

• Weight loss

• Sinus tachycardia•  trial fibrillation 0apathetic hyperthyroidism in the elderly1

HYPERTHYROIDISM

Etiology• 2ra!es3 disease

• Nodular toxic goiter

• Subacute thyroiditis

• 4actitious

• #ituitary tumors

HYPERTHYROIDISM

Clinical features• Diarrhea

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• Warm, moist s$in

• 5estlessness and tremor

• /phthalmic findings& lid lag and the hyperthyroid 6stare7

• %hyroid exophthalmos& seen only in 2ra!es8 disease9 due to infiltration of

the extraocular muscles

HYPERTHYROIDISM

Tyroid storm• Se!ere exacerbation of hyperthyroidism

• /ften precipitated by infection, surgery, or deli!ery

• +igh fe!ers, tachycardia with associated high mortality

HYPERTHYROIDISM

&a'oratory studies• *le!ated total %( and %)

• *le!ated %) resin upta$e

• *le!ated radioacti!e iodine upta$e• 'ow %S+

HYPERTHYROIDISM

Treatment•  ntithyroid drugs• "ethimaole and propylthiouracil 0#%1

o Decrease the synthesis of thyroid hormone by inhibiting the

oxidation of iodideo #% also inhibits the con!ersion of %( to %)

o S$in rash, :oint pain, or agranulocytosis may occur

HYPERTHYROIDISM

Treatment• "ethimaole and propylthiouracil 0#%1o  llows out-patient therapy

o 'ess li$elihood of subse;uent hypothyroidism

• Beta-bloc$ers& do not affect thyroid function but will bloc$ adrenergic effects

of hyperthyroidism

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HYPERTHYROIDISM

Treatment• Subtotal thyroidectomy

o  llows for cure of hyperthyroidism

o #atient compliance with long-term medication is necessaryo 'ess hypothyroidism than with radioacti!e iodine

o #atient should be euthyroid before surgery

HYPERTHYROIDISM

Treatment• 5adioacti!e iodine

o "ost patients re;uire < or = doses of radioacti!e iodine to cause

decrease in function and sieo  llows outpatient treatmento Very high success rate

HYPERTHYROIDISM

Treatment•  fter years, up to half of patients may become hypothyroid and re;uire

thyroid hormone replacement• No increase in leu$emia ris$, thyroid cancer, or other malignancies9 slight

ris$ of genetic defects in offspring

HYPERTHYROIDISM

Treatment of tyroid storm• ?V sodium iodide inhibits the release of thyroid hormones

•  ntithyroid drugs bloc$ further hormone synthesis

• Beta-bloc$ers bloc$ peripheral effects of thyroid hormone