Hyperthyroidism is defined as a hypermetabolic state that is characterized by elevated peripheral thyroid hormones.
- Subclinical hyperthyroidism: low TSH levels in the setting of normal free peripheral thyroid hormone levels (T3, T4).
- Overt hyperthyroidism: low TSH is seen in the setting of elevated T3 and/or T4.
As always, a thorough medical history and physical exam is important to establishing the diagnosis. Risk factors that place patients at increased risk of Hyperthyroidism include:
- female gender,
- positive family history,
- other autoimmune disease,
- iodide repletion after deprivation.
Signs and symptoms of hyperthyroidism are the result of stimulation of the adrenergic nervous system, and can include nervousness, heat sensitivity, palpitations, dyspnea, tachycardia, weight loss, goiter and/or thyroid tenderness. Elderly patients may also exhibit CHF and/or atrial fibrillation.
Causes of hyperthyroidism include:
- Grave’s disease (80-90% of cases): Autoimmune disease resulting from thyroid-stimulating antibodies binding to TSH receptors. Diagnosis is confirmed by elevated thyroid hormones and increased homogenous radioactive iodine uptake. Thyroid-stimulating antibody levels are also increased.
- Toxic Multi (and Uni-) Nodular goiter: Diagnosed by thyroid scan (with increased heterogeneous uptake) and/or biopsy.
- Iatrogenic and factitious
- Hypersecretion of TSH
- Amiodarone therapy
Defined by: Andrew R. Crichlow, MD