Thyroid: What Is TSH?

Thyroid-stimulating hormone, or TSH, is an important trigger for the thyroid gland to function properly.

Located at the base of the neck, the thyroid gland is the control center for the body’s metabolism. It uses iodine in the body to produce two hormones, triiodothyronine (T3) and thyroxine (T4), said WebMD.

The thyroid and the pituitary gland work together. When the pituitary gland produces its TSH, it triggers the thyroid gland to produce more T3 and T4 which are responsible for many bodily functions.

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According to Healthline, a physician might order a simple blood test called a TSH test to assess the levels of thyroid-stimulating hormone in the blood if a thyroid disorder is suspected.

The thyroid gland can either produce too much (hyperthyroidism) or too little thyroid hormone (hypothyroidism). The thyroid gland and the pituitary gland work on a feedback loop with one another, so measuring levels of TSH can confirm a thyroid disorder.

The normal range for TSH is between 0.4 to 4.0 milli-international units per liter of blood.

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When the TSH levels in the blood are higher than the normal range, it can indicate hypothyroidism. Because the thyroid gland isn’t producing enough T3 and T4, the pituitary gland responds by making more TSH in an effort to trigger more thyroid hormone production.

When the TSH levels are below the normal range, this indicates hyperthyroidism. The thyroid is producing too much thyroid hormone, so the pituitary gland makes less TSH in response.

The TSH test is a valuable one, but it must be considered in combination with other diagnostic tools to confirm a thyroid disorder. Results of the TSH can be artificially skewed by unrelated factors such as first-trimester pregnancy, recent X-ray studies, certain medications, stress, and chronic illness.

According to WebMD, a TSH test is the most effective screening tool for thyroid disorders, but most physicians will also order a thyroid hormone test to cross check the TSH test results.

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