Thyroid-Stimulating Hormone (TSH)

This test measures thyroid-stimulating hormone (TSH), a signal from the pituitary gland that tells your thyroid how much hormone to produce. Thyroid hormones help regulate energy, metabolism, and body temperature. TSH is commonly the first test used to assess thyroid function and can help identify an underactive thyroid (hypothyroidism) or an overactive thyroid (hyperthyroidism). Testing may help investigate fatigue, unexplained weight changes, sensitivity to heat or cold, bowel changes, or a racing heartbeat.