TSH is an acronym that stands for thyroid-stimulating hormone, notes WebMD. The level of TSH in the blood is checked when ruling out or diagnosing problems with the thyroid gland.
TSH is released by the hypothalamus, and testing TSH levels is useful in determining whether or not the thyroid gland is functioning as it should, reports WebMD. TSH levels are used to diagnosis both underactive or hypothyroid conditions as well as overactive or hyperthyroid conditions. For adults, the normal TSH level is 0.4 to 4.2 microunits per milliliter, and for children, the normal level is 0.7 to 6.4 microunits per mililiter.
TSH is responsible for the thyroid gland’s production of two hormones, T3 and T4, which help control metabolism and are necessary for normal brain growth. T3 and T4 levels may be tested at the same as the TSH level, according to WebMD.
TSH-level tests are administered to help determine whether the thyroid gland is working properly, says WebMD. An overactive thyroid is known as hyperthyroidism and can cause rapid heart rate, weight loss, nervousness, irregular menstrual periods and several other health problems. An underactive thyroid, known as hypothyroidism, can cause fatigue, weight gain, constipation and dry skin.
TSH levels may also be tested to find the cause of an underactive thyroid gland, explains WebMD. TSH levels can tell a doctor whether an underactive thyroid is caused by damage to the thyroid gland or another cause, such as a problem with the hypothalamus or pituitary gland. High TSH levels may indicate hypothyroidism, a tumor on the pituitary gland or a dosage of thyroid hormone medicine that is too small, while low levels may indicate hyperthyroidism, pituitary gland damage, benign thyroid nodule or that the patient is taking too much thyroid medicine.