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Hyperthyroidism or thyrotoxicosis is composed of a spectrum of clinical findings consistent with thyroid hormone excess. The former describes excess from the thyroid gland, whereas the latter can be produced from any other source.
- Graves disease (GD): The most common form; diffuse goiter and thyrotoxicosis are common characteristics. Infiltrative orbitopathy is seen in 50% of patients. Infiltrative dermopathy is rare. Autoantibodies are directed at the thyrotropin-stimulating hormone (TSH) receptors.
- Toxic multinodular goiter (TMNG): 2nd most common; a TSH receptor mutation has been found in 60% of patients; patients age >40 years, insidious onset, frequent in iodine-deficient areas
- Toxic adenoma: Younger patients, autonomously functioning nodules
- Iodine-induced hyperthyroidism
- Thyroiditis: Transient autoimmune process:
- Subacute thyroiditis/De Quervain: Granulomatous giant cell thyroiditis, benign course; viral infections have been involved.
- Postpartum thyroiditis
- Drug-induced thyroiditis: Amiodarone, interferon-α, interleukin 2, lithium
- Miscellaneous: Thyrotoxicosis factitia, TSH-secreting pituitary tumors, and functioning trophoblastic tumors
- Subclinical hyperthyroidism: Suppressed TSH with normal thyroxine (T4); may be associated with osteoporosis and atrial fibrillation (1).
- Thyroid storm: Rare hyperthyroidism; fever, tachycardia, systolic hypertension, CNS dysfunction (e.g., coma); up to 50% mortality
- Characteristic symptoms and signs may be absent.
- Atrial fibrillation is common when TSH <0.1 mU/L.
- Neonates and children are treated with antithyroids for 12–24 months.
- Radioactive iodine is controversial in patients under the ages of 15–18 years.
Propylthiouracil (PTU) is currently the drug of choice during pregnancy. Treat with lowest effective dose. Avoid treatment-induced hypothyroidism. Radioiodine therapy is contraindicated.
- 1.3% of population
- Predominant sex: Female > Male (7–10:1).
- Predominant age: Autoimmune thyroid disease in 2nd and 3rd decades. TMNG presents in patients >40 years. GD is seen between 40 and 60 years of age.
- Female 1/1,000
- Male: 1/3,000
- Positive family history, especially in maternal relatives
- Other autoimmune disorders
- Iodide repletion after iodide deprivation, especially in TMNG
Concordance rate for GD among monozygotic twins is 35%.
- GD: Autoimmune disease
- TMNG: 60% TSH receptor gene abnormality; 40% unknown
- Toxic adenoma: Point mutation in TSH receptor gene with increased hormone production
- Hashitoxicosis: Autoimmune destruction of the thyroid; antimicrosomal antibodies present
- Subacute/De Quervain thyroiditis: Granulomatous reaction; genetic predisposition in specific HLAs; viruses, such as coxsackievirus, adenovirus, echovirus, and influenza virus, have been implicated; self-limited course, 6–12 months
- Suppurative: Infectious
- Drug-induced thyroiditis: Amiodarone produces an autoimmune reaction and a destructive process. Lithium, interferon-α, and interleukin 2 cause an autoimmune thyroiditis.
- Postpartum thyroiditis: Autoimmune thyroiditis that lasts up to 8 weeks and, in 60% of patients, hypothyroidism manifests in the future.
Commonly Associated Conditions
- Autoimmune diseases
- Down syndrome
- Iodine deficiency