Heat Intolerance
Heat intolerance — feeling uncomfortably hot in situations others find fine, excessive sweating, or strong aversion to warmth — is a recognised symptom of thyroid overactivity.
It is not specific, however; several other conditions cause similar symptoms.
Last medically reviewed: 1 November 2025
Thyroid mechanism
Excess thyroid hormone raises metabolic rate and heat production. The body responds with sweating and vasodilation — patients feel hot, sweat more and may have warm, moist skin.
Heat intolerance often accompanies weight loss, palpitations, tremor and anxiety in hyperthyroidism.
Other causes
Menopause and perimenopause (hot flushes), anxiety, infections/fever, medications (some antidepressants, blood pressure drugs), caffeine, hyperhidrosis, and pheochromocytoma (rare) all cause heat intolerance.
In women, menopausal hot flushes are a very common alternative explanation.
When to test
Thyroid testing is worthwhile when heat intolerance is accompanied by other hyperthyroid features, is new or worsening, or occurs alongside weight loss, palpitations or tremor.
A normal TSH effectively excludes significant thyroid overactivity as the cause.
Frequently asked questions
Is heat intolerance a sign of hyperthyroidism?
It can be — along with weight loss, palpitations and tremor — but it is not specific. Testing confirms whether thyroid is involved.
Can hypothyroidism cause cold intolerance instead?
Yes — hypothyroidism typically causes cold intolerance (feeling cold when others are comfortable), the opposite pattern. Both are evaluated with the same thyroid tests.
What about hot flushes vs thyroid?
Menopausal hot flushes are episodic, often with sweating and flushing, and common in women 45–55. Thyroid-related heat intolerance tends to be more constant. Thyroid testing distinguishes them.
References & further reading
This page is based on established medical knowledge and guidelines from authoritative sources. Always consult a qualified clinician for personal medical advice.
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