Thyroid Stimulating Hormone (TSH) Blood Test

TSH is produced by the pituitary gland in your brain. The TSH test measures the level of thyroid-stimulating hormone in your blood. It can tell you if it’s overactive (hyperthyroidism) or underactive (hypothyroidism).

The TSH has a normal test range between 0.4 and 4.0 milli-international units of hormone per liter of blood (mIU/L). If you show signs of hypothyroidism and have a TSH reading above 2.0 mIU/L, you're at risk for progressing to hypothyroidism.

The test can also detect a thyroid disorder before you have any symptoms. If untreated, a thyroid disorder can cause health problems.

What happens if TSH level is high?

If your TSH levels are abnormally high, it could mean you have an underactive thyroid, or hypothyroidism. That's because it indicates your pituitary gland is producing more TSH in an effort to stimulate your thyroid to produce thyroid hormone.

Hypothyroidism signs and symptoms may include:

• Fatigue.
• Increased sensitivity to cold.
• Constipation.
• Dry skin.
• Weight gain.
• Puffy face.
• Hoarseness.
• Muscle weakness.

What happens if TSH level is low?

Low TSH is most often associated with hyperthyroidism. This can be due to a number of causes, ranging from autoimmune disease to lumps in the thyroid gland (toxic nodules) to an abnormally enlarged thyroid gland (goiter).

Symptoms of low TSH include:

• Weight loss.
• Fatigue.
• Confusion.
• Heat intolerance.
• Fast heartbeat.
• High blood pressure and other symptoms.