What is the nature of the relationship between the thyroid and the parathyroid glands? Name the hormones secreted by each and the targets of these hormones?
The thyroid, located on the trachea below the larynx, secretes thyroxin and triiodothyrinine. Called the thyroid hormones (TH), these two hormones stimulate all tissues' oxidative metabolism and help to regulate the development of the body. The thyroid also secretes calcitonin which prevents the excessive rise of calcium levels in the blood, thus, balancing the activities of the parathyroid hormone (PTH). Secreted by the parathyroids, four pea-sized organs located on the surface of the thyroid but which are both developmentally and functionally distinct from the thyroid, PTH elevates blood-calcium levels and decreases blood-phosphate levels. PTH acts on the kidneys to re absorb more calcium into the blood and excrete more phosphate, on the intestine to re absorb more calcium into the blood, and on the bones to release calcium into the blood.
