Free Triiodothyronine [FT3] : The amount of the T3 hormone in blood indicates over or underactivity of the thyroid gland. High T3 levels may indicate over-function of thyroid gland while reduced levels may be indicative of underactivity of thyroid, known as hypothyroidism.
Free Thyroxine (FT4) : Thyroxine is the hormone secreted by your thyroid gland. T4 levels in blood are used to determine over or underactivity of the thyroid gland. The most common cause of thyroid dysfunction is autoimmune disease. Graves’ disease causes hyperthyroidism (overactivity) and Hashimoto thyroiditis causes hypothyroidism (underactivity).
TSH (Ultrasensitive), (Thyroid Stimulating Hormone - Ultrasensitive). As the name suggests TSH is a hormone that stimulates the thyroid gland to secrete hormones. Thyroid gland is a butterfly shaped gland present in the middle part of the neck, and produces hormones that control various body functions :
Levels of TSH in blood may indicate under- and over-activity of the thyroid gland. However, the TSH levels may vary in a normal individual.