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.
Hormones may be regulated by other hormones, by glands and organs, and by a negative feedback mechanism. Hormones that regulate the release of other hormones are called tropic hormones. The majority of tropic hormones are secreted by the anterior pituitary in the brain. The hypothalamus and thyroid gland also secrete tropic hormones. The hypothalamus produces the tropic hormone thyrotropin-releasing hormone (TRH), which stimulates the pituitary to release thyroid stimulating hormone (TSH).