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Source: Jonklaas J, Talbert RL. Thyroid Disorders. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, eds. Pharmacotherapy: A Pathophysiologic Approach. 8th ed. http://accesspharmacy.com/content.aspx?aid=7991868. Accessed June 22, 2012.

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  • Thyrotoxicosis
  • Overactive thyroid

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  • Clinical and biochemical syndrome resulting from increased thyroid hormone production.

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  • TSH-secreting pituitary adenomas
  • Graves’ disease
  • Trophoblastic diseases
  • Thyroid autonomy
  • Toxic adenoma
  • Multinodular goiter
  • Subacute thyroiditis
  • Painless thyroiditis
  • Ectopic thyroid tissue
  • Struma ovarii
  • Exogenous thyroid hormone sources
  • Medications
  • Foods

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  • Thyrotoxicosis results when tissues exposed to excessive levels of thyroxine (T4), triiodothyronine (T3), or both.
  • TSH-secreting pituitary tumors release active hormone unresponsive to normal feedback control.
  • In Graves’ disease, hyperthyroidism results from action of thyroid-stimulating antibodies (TSAb).
  • Autonomous thyroid nodule (toxic adenoma) is thyroid mass whose function is independent of pituitary control.
  • In multinodular goiters, follicles with autonomous function generate more thyroid hormone than required.
  • Painful subacute thyroiditisoften develops after viral illness.
  • Painless thyroiditis may have underlying autoimmune cause.
  • Amiodarone may induce thyrotoxicosis and may also cause destructive thyroiditis with loss of thyroglobulin and thyroid hormones.

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  • In National Health and Nutrition Examination Survey III:
    • 0.7% of those surveyed had subclinical hyperthyroidism and 0.5% had clinically significant hyperthyroidism.
    • Prevalence of suppressed TSH peaked for people aged 20–39, declined in those 40–79, and increased again in those 80 or older.
    • Abnormal TSH levels were more common among women than men.

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Signs and Symptoms

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  • Symptoms:
    • Nervousness
    • Anxiety
    • Palpitations
    • Emotional lability
    • Easy fatigability
    • Heat intolerance
    • Weight loss with increased appetite
    • Increased frequency of bowel movements
    • Proximal muscle weakness
    • Scanty or irregular menses in women
  • Signs:
    • Thyroid enlargement
    • Exophthalmos
    • Pretibial myxedema
    • Warm, smooth, moist skin and unusually fine hair
    • Onycholysis
    • Lid lag
    • Resting tachycardia, widened pulse pressure, and systolic ejection murmur
    • Gynecomastia in men
    • Fine tremor of protruded tongue and outstretched hands
    • Hyperactive deep tendon reflexes
  • Thyroid storm:
    • Decompensated thyrotoxicosis
    • High fever (often above 39.4°C [103°F])
    • Tachycardia
    • Tachypnea
    • Dehydration
    • Delirium
    • Coma
    • Nausea
    • Vomiting
    • Diarrhea

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Laboratory Tests

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  • TSH, total T4, free T4, T3 resin uptake, free thyroxine index, 24-hour radioactive iodine uptake (RAIU).

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Imaging

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  • Thyroid scan shows areas of autonomously functioning thyroid tissue in multinodular goiters.

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Differential Diagnosis

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  • General anxiety disorder, panic disorder, mania
  • Other hypermetabolic states (e.g., cancer, pheochromocytoma)
  • Hypopituitarism
  • Subclinical hyperthyroidism

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  • Eliminate excess thyroid hormone.
  • Minimize symptoms and long-term consequences.
  • Provide individualized therapy based on:
    • Disease type and severity
    • Patient age and sex
    • Existence of nonthyroid conditions
    • Response to previous therapy

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  • Consider thyroidectomy if on antithyroid drug treatment and:
    • Large gland (>80 g)
    • Severe ophthalmopathy
    • Lack of remission

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  • Thioureas (propylthiouracil [PTU], methimazole)
    • Usual initial doses:
      • PTU 300–600 mg daily, usually in 3 or 4 divided doses
      • Methimazole 30–60 mg daily in 3 divided doses
    • Improvement observed within 4–8 weeks, then start tapering regimen to maintenance doses (e.g., PTU 50–300 mg, methimazole 5–30 mg).
    • Change dosages approximately once monthly ...

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