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.
For example, the pituitary gland (endocrine gland) secretes thyroid-stimulating hormone, which acts on the target organ, the thyroid gland, to stimulate production of the thyroid hormones T3 and T4.The pituitary then monitors the circulating levels of thyroid hormones.n negative feedback, the endocrine gland has a natural tendency to over-secrete its hormone. The hormone then stimulates the target tissue to perform a function. Thus, the important factor is not the rate of secretion of the hormone but the rate that the target function is performed.