Heat intolerance

An impaired thermoregulatory response to heat, leading to disproportionate hyperthermia, tachycardia, and heat-stress symptoms. Possible causes are hyperthyroidism, Graves' disease, multiple sclerosis, autonomic nervous system dysfunction, hormonal fluctuations/menopause, medications (antidepressants, antihistamines, amphetamines, caffeine, decongestants, diuretics), diabetes, obesity, and alcohol abuse.