Your Body's Energy Regulator - Thyroid Stimulating Hormone (TSH) Test

The thyroid-stimulating hormone (TSH) test measures the level of this hormone in the blood serum. TSH is secreted by the pituitary gland in the brain and regulates the thyroid gland by signaling it to release its hormones (T4 and T3). TSH is considered the most sensitive indicator for detecting thyroid dysfunction, as it is elevated in cases of hypothyroidism (primary hypothyroidism) and decreased in cases of hyperthyroidism (primary hyperthyroidism).