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ULY CLINIC
ULY CLINIC
11 Septemba 2025, 05:55:58
Heat intolerance
Heat intolerance is the inability to tolerate elevated environmental temperatures or to maintain normal body temperature, resulting in persistent sensations of overheating and, often, profuse sweating (diaphoresis). It typically develops gradually and can range from mild discomfort to debilitating sensitivity, interfering with daily activities.
Thermoregulation is controlled by the hypothalamus, which integrates signals from peripheral thermoreceptors, endocrine hormones, and the autonomic nervous system. Dysfunction in any of these systems—through excess heat production, impaired dissipation, altered hypothalamic set point, or hormonal fluctuations—can manifest as heat intolerance. Thyrotoxicosis, menopause, hypothalamic lesions, and certain medications are common causes. Prompt identification of the underlying etiology is crucial for management and to prevent complications such as dehydration, electrolyte imbalances, or heat-related illnesses.
Pathophysiology
Mechanism | Description |
Excess Heat Production | Thyrotoxicosis increases basal metabolic rate and mitochondrial activity, producing more heat. |
Impaired Heat Dissipation | Anticholinergic drugs, dehydration, or sweat gland dysfunction reduce evaporative cooling. |
Altered Hypothalamic Set Point | Lesions or tumors disrupt the body’s temperature “thermostat,” causing abnormal heat perception. |
Hormonal Fluctuations | Menopause-related estrogen decline alters hypothalamic thermoregulation, causing hot flashes. |
Causes of heat intolerance
Category | Specific Cause | Clinical Features / Distinguishing Signs |
Endocrine | Thyrotoxicosis | Persistent heat intolerance, warm/flushed skin, diaphoresis, weight loss with increased appetite, tremor, tachycardia, palpitations, nervousness, diarrhea, lid lag, possible exophthalmos |
Menopause | Hot flashes, night sweats, flushing, mood swings, insomnia, weight gain; episodes are usually brief (minutes) | |
Central / Neurologic | Hypothalamic Disease | Alternating heat/cold intolerance, sleep disturbances, amenorrhea, polyuria/polydipsia, personality changes; caused by pituitary adenomas, hypothalamic or pineal tumors |
Drugs / Medications | Amphetamines, amphetamine-like appetite suppressants, excessive thyroid hormone, anticholinergics | Onset related to drug use; anticholinergics impair sweating, producing heat retention |
Pediatric / Neonatal | Maternal thyrotoxicosis, acquired thyrotoxicosis in adolescents | Rare; dehydration can worsen symptoms; may present with irritability and heat sensitivity |
Other Causes | Fever, infection, hypermetabolic states | Often transient; accompanied by other systemic symptoms (e.g., tachycardia, malaise) |
Types of Heat intolerance
Type | Key Features | Notes / Distinguishing Findings |
Thyrotoxicosis-related | Chronic heat intolerance, diaphoresis, palpitations, weight loss, nervousness | Multi-system involvement; may have thyroid enlargement or exophthalmos |
Menopause-related | Episodic hot flashes, flushing, night sweats | Hormone-related, brief episodes |
Hypothalamic / Central | Alternating heat/cold intolerance, sleep disturbance, personality changes | Often associated with tumors or lesions affecting hypothalamus/pituitary |
Drug-induced | Rapid onset after medication use | Reversible upon drug adjustment |
Pediatric / Neonatal | Rare, heat sensitivity in children/adolescents | May result from maternal thyroid disorder or dehydration |
History and physical examination
History
Onset, severity, and duration of heat intolerance
Sweating patterns, ability to tolerate warm environments
Clothing preference, use of air conditioning
Changes in appetite, weight, mood, or personality
Medications (thyroid drugs, amphetamines, anticholinergics)
Family or personal history of endocrine or hypothalamic disorders
Physical examination
Assess clothing, vital signs, skin (flushing, diaphoresis), tremor, lid lag
Evaluate thyroid size, nodules, or exophthalmos
Neurological examination if central lesion suspected
Hydration status, signs of systemic involvement
Management and Patient counseling
Environmental adjustments: Maintain a cool environment; encourage light clothing
Hydration: Adequate fluid intake to prevent dehydration
Medication review: Adjust or discontinue causative drugs under medical supervision
Education: Discuss underlying cause, preventive strategies, and importance of monitoring symptoms
Specific interventions: Treat underlying endocrine or central disorders; manage menopausal symptoms
Special considerations
Pediatric patients: Rarely affected; dehydration can worsen symptoms
Geriatric patients: Age-related thermoregulatory changes can amplify heat intolerance
References
Brothers, R. M., Wingo, J. E., Hubing, K. A., & Crandall, C. G. (2009). The effects of reduced end-tidal carbon dioxide tension on cerebral blood flow during heat stress. Journal of Physiology, 587, 3921–3927.
Bundgaard-Nielsen, M., Wilson, T. E., Seifert, T., Secher, N. H., & Crandall, C. G. (2010). Effect of volume loading on the Frank-Starling relation during reductions in central blood volume in heat-stressed humans. Journal of Physiology, 588, 3333–3339.
Wieringa, F. T., Dijkman, J., & Mensink, G. B. (2012). Thermoregulation and endocrine disorders: clinical considerations. Endocrine Reviews, 33(1), 1–25.
Morley, J. E., & Kaiser, F. E. (2000). Heat intolerance and thyroid dysfunction: pathophysiology and clinical implications. Journal of Clinical Endocrinology & Metabolism, 85(10), 3740–3747.
Shanafelt, T. D., Barton, D. L., & Adjei, A. A. (2002). Management of hot flashes in patients with endocrine disorders. Mayo Clinic Proceedings, 77(4), 359–368.