Cancer*

Lymphoma, leukemia

Central nervous system

Trauma, autonomic neuropathy

Medications and substances

Antidepressants, aspirin, nonsteroidal anti-inflammatory drugs, hypoglycemic agents, caffeine, theophylline; opioid withdrawal

Endocrine disorders

Hyperthyroidism, hypoglycemia, excessive secretion of sex hormones caused by gonadotropin-releasing hormone (GnRH) agonists

Idiopathic

—

Infections*

Tuberculosis, endocarditis, systemic fungal infections

Other

Carcinoid syndrome, pregnancy, menopause, anxiety, fever