Thyroid Stimulating Hormone (TSH) - Serum

What Is Thyroid Stimulating Hormone (TSH)?

Thyroid-stimulating hormone (TSH) is a hormone produced by your pituitary gland in the brain. It signals your thyroid gland to produce and release thyroid hormones, which play a key role in metabolism, energy, and overall body function. TSH levels can help identify whether your thyroid is underactive (hypothyroidism) or overactive (hyperthyroidism).

Why Is a TSH Test Done?

Your doctor may order a TSH test if you have symptoms like fatigue, weight changes, unexplained hair loss, or mood swings. It’s also used as part of routine check-ups, especially in older adults or those with a family history of thyroid disorders. Sometimes, TSH is checked alongside other thyroid tests if symptoms or lab results suggest thyroid issues.

What Does a TSH Test Tell You?

A TSH test provides a snapshot of your thyroid function. High TSH levels may indicate hypothyroidism (low thyroid activity), while low TSH levels may suggest hyperthyroidism (overactive thyroid). Normal results usually mean your thyroid is functioning within a healthy range, but doctors may still recommend further testing if needed.

How Is the TSH Test Performed?

A blood sample is taken from a vein in your arm, usually in a doctor’s office or lab. The sample is sent to a lab where TSH levels are measured using an immunoassay method. The process is quick and typically requires no special preparation, though fasting may be advised in some cases.