Palpitations in hyperthyroidism are caused by increased sympathetic activity and elevated metabolic rate. Tremors are a common accompanying symptom due to enhanced beta-adrenergic receptor sensitivity in the nervous system. This manifests as fine, rapid shaking of the hands. In contrast, bradycardia, weight gain, and constipation are typically seen in hypothyroidism, not hyperthyroidism. Recognizing tremors alongside palpitations helps confirm the hyperthyroid state clinically.

Reference: Harrison's Principles of Internal Medicine, Fauci et al., 20th Edition.