Simple vs Complex Endocrine Loops

A simple endocrine loop is one that involves only one hormone and maintains homeostasis. Most loops are stimulated by a humoral stimuli, or a change in interstitual fluid. An example of a simple endocrine loop is the parathyriod hormone. When there is a decrease in blood calcuim, the parathyroid glad acts as a sensor and control center, recognizing the change and signalling to an effort tissue. The effector, the parathyroid gland, releases the parathyroid hormone, which effects the bones, kidneys, and digestive tract. In the bones, osteoclasts break down bone and release calcium. The kidneys and digestive tract increase calcium reabsorption. Calcium levels increase in the blood until the normal level of blood calcium is achieved. A complex endocrine loop uses multiple hormones and has varied responses. For example, thyroid hormone is released when the body needs to increase metabolism. The signal goes to the hypothalamus which produces thyroid releasing hormone, which stimulates the anterior pituitary gland. The anterior pituitary glad then relases thyroid stimulating hormone which stimulates the thyriod gland to release thyroid hormone. Thyroid hormone stimulates every cell in the body with a receptor for thyroid hormone to increase metabolism, heat generation, and growth and devlopment.