1 The phenotype may change constantly throughout the life of an individual because of environmental changes and the physiological and morphological changes associated with aging.
One special group of hormones is the tropic hormones that stimulate the hormone production of other endocrine glands. For example, thyroid-stimulating hormone (TSH) causes growth and increased activity of another endocrine gland, the thyroid, which increases output of thyroid hormones. hormone (from Greek á½ÏÎ¼Î®, impetus) is any member of a class of signaling molecules produced by glands in multicellular organisms that are transported by the circulatory system to target distant organs to regulate physiology and behaviour.
Thyroid-stimulating hormone (TSH) is produced by the pituitary gland, a tiny organ located below the brain and behind the sinus cavities. TSH stimulates the thyroid gland to release the hormones thyroxine (T4) and triiodothyronine (T3) into the blood. These thyroid hormones help control the rate at which the body uses energy. This test measures the amount of TSH in the blood. TSH, along with its regulatory hormone thyrotropin releasing hormone (TRH), which comes from the hypothalamus, is part of the feedback system that the body uses to maintain stable amounts of thyroid hormones in the blood.