Causes

Common causes of hyperthyroidism are Graves' disease, toxic multinodular goiter, toxic adenoma, and subacute thyroiditis.

Clinical presentation

The clinical presentation is the same regardless of underlying cause. Symptoms include anxiety, nervousness, emotional lability, sweating, heat insensitivity, palpitations, fatigue, weight loss, irregular or fast heartbeat, muscle wasting and weakness, and increased bowel movements.64 Signs include tachycardia, warm and moist skin, enhanced physiologic tremor, lid retraction and lag, rapid speech, hyperactivity, and proximal muscle weakness. Chorea may be seen,65 and a goiter may be present, depending on the cause. Exophthalmos is present only in patients with Graves' disease.

In patients with established epilepsy (including generalized epilepsy syndromes), seizures and paroxysmal EEG abnormalities can be exacerbated by hyperthyroidism.66,67 In other patients, focal or generalized seizures occur only during thyrotoxic episodes.68 Seizure exacerbations usually remit when patients become euthyroid with treatment.

Evaluation

The diagnosis is confirmed by low serum thyroid-stimulating hormone (TSH) and high concentrations of T4, T3, or both.

The electrocardiogram (ECG) often shows atrial fibrillation.

Adapted from: Schachter SC and Lopez MR. Metabolic disorders. In: Ettinger AB and Devinsky O, eds. Managing epilepsy and co-existing disorders. Boston: Butterworth-Heinemann; 2002;195–208. With permission from Elsevier (www.elsevier.com).

Reviewed and revised April 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.