Hyperthyroidism

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.

• Thyrotoxicosis
• Overactive thyroid

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

• 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

• 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.

• 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.

Signs and Symptoms

• 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

Laboratory Tests

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

Imaging

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

Differential Diagnosis

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

• 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

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

• 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 ...