TSH stands for Thyroid-Stimulating Hormone, which is a hormone produced by the pituitary gland in the brain. TSH plays an important role in regulating the thyroid gland's production of the hormones T3 (triiodothyronine) and T4 (thyroxine), which are important for metabolism, growth, and development.

A TSH blood test is used to measure the amount of TSH in the blood and is often used as a screening test for thyroid disorders. High levels of TSH may indicate an underactive thyroid gland, known as hypothyroidism, while low levels of TSH may indicate an overactive thyroid gland, known as hyperthyroidism.

Symptoms of hypothyroidism may include fatigue, weight gain, cold intolerance, and depression, while symptoms of hyperthyroidism may include weight loss, rapid heart rate, sweating, and anxiety. Treatment for thyroid disorders may involve medication, dietary changes, or, in some cases, surgery.