Thyroid disorders are common, often subtle, and frequently missed as a cause of sleep and energy problems. An underactive thyroid (hypothyroidism) can cause fatigue, cold intolerance, and fragmented sleep, while an overactive thyroid (hyperthyroidism) can cause insomnia, heat intolerance, and a racing heart at night. Because the symptoms overlap with many other conditions, the thyroid is worth checking when sleep and energy are off without a clear explanation.





