Everlywell Thyroid Test

Thyroid-stimulating hormone, or TSH, is a hormone produced by the pituitary gland that is responsible for controlling the production of the thyroid hormones T3 and T4 by the thyroid gland. The hormone TSH is considered the most sensitive marker for screening for thyroid diseases and conditions.

Thyroid peroxidase antibodies are antibodies that can bind to thyroid enzymes, suppressing thyroid function. If TPO antibodies are elevated, this could be suggestive of an autoimmune condition. In the case of hypothyroidism, or an underactive thyroid, Hashimoto’s thyroiditis may be the culprit, whereas hyperthyroidism, or an overactive thyroid is commonly caused by Graves’ disease.

T3 (triiodothyronine) is a hormone produced by the thyroid gland. While it is less abundant than T4, T3 is considered the more active of these two thyroid hormones. Together, these two thyroid hormones help determine the rate at which every cell in the body uses energy. Levels of T3 fluctuate when individuals have an under- or overactive thyroid gland. This test measures free T3, the free (not bound to protein), and biologically active form of the hormone.

T4 (thyroxine) is the predominant hormone produced by the thyroid gland. Together, T3 and T4 help determine the rate at which every cell in the body uses energy. Levels of T4 fluctuate when individuals have an under- or overactive thyroid gland. This test measures free T4, the free (not bound to protein), and biologically active form of the hormone.