Thyroid-stimulating hormone (TSH or thyrotropin) is a glycoprotein produced by the anterior pituitary gland and is made up of two subunits. The (alpha) subunit is identical to that of human chorionic gonadotropin (hCG), luteinizing hormone (LH), and follicle-stimulating hormone (FSH), whereas the (beta) subunit is unique to TSH and determines its function. TSH production and release is controlled by thyrotropin releasing hormone (TRH). Somatostatin has an inhibitory effect on TSH production. TSH stimulates the thyroid gland to secrete the hormones thyroxine (T4) and triiodothyronine (T3) into the blood stream. Cayman's human Thyroid-Stimulating Hormone EIA Kit is an immunometric (i.e., sandwich) EIA which can be used to measure TSH within the range of 0.2 mIU/L to 20 mIU/L. This assay offers specific and sensitive analysis of TSH in human serum and plasma, and has not been validated for other types of samples.