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.
The hormones parathyroid hormone (PTH) and calcitonin help regulate blood calcium levels. Calcitonin, secreted by the thyroid gland inhibits osteoclasts and stimulates osteoblasts, thus decreasing blood calcium levels. Parathyroid hormone is secreted by the parathyroid glands, which are on the posterior side of the thyroid. Parathyroid hormone inhibits osteoblasts, stimulates osteoclasts, reduces the output of calcium by the kidneys and promotes the absorption of calcium by the small intestines, thus increasing blood calcium levels.