Thyroid stimulating hormone (TSH) is produced and secreted by the pituitary gland and stimulates the thyroid to make T3 and T4. When TSH is elevated, low thyroid function may be indicated. When TSH is low, it is indicative of high thyroid function. TSH is used as a first line screening tool to assess thyroid disease; however, is best utilized when evaluated in conjuction with other thyroid markers such as T3, T4, thyroid antibodies, etc. Additionally, health care providers check TSH to monitor disease progression and treatment. Fasting is not required for this test. Take all medications as prescribed.