(TFTs) Usually two tests: a serum thyroxine (low for underactivity, high for overactivity) and a serum thyroid stimulating hormone (TSH, high for underactivity based primarily in the thyroid gland, low for overactivity based primarily in the thyroid gland and low for underactivity based in the pituitary gland). As a screening test for malfunction of the thyroid gland a serum TSH will generally be enough.

The main hormone of the thyroid gland, responsible for controlling the rate of metabolism in the body; activity of the thyroid gland is measured with thyroid function tests.