Thyroid hormone secretion is regulated by a negative feedback mechanism that involves the amount of circulating hormone , hypothalamus , and adenohypophysis. If there is an iodine deficiency , the thyroid cannot make sufficient hormone. This stimulates the anterior pituitary to secrete thyroid-stimulating hormone , which causes the thyroid gland to increase in size in a vain attempt to produce more hormones.
But it cannot produce more hormones because it does not have the necessary raw material, iodine. This type of thyroid enlargement is called simple goiter or iodine deficiency goiter. Calcitonin is secreted by the parafollicular cells of the thyroid gland.
This hormone opposes the action of the parathyroid glands by reducing the calcium level in the blood. Moreover, lower levels of parathyroid hormone lead to hypothyroidism, which results in lower calcium levels in the blood.
On the other hand, higher levels of parathyroid hormone lead to hyperthyroidism, which results in higher calcium levels in the blood. Calcitonin refers to a peptide hormone secreted by parafollicular cells also known as C cells of the thyroid gland in humans, and in many other animals while parathyroid hormone refers to a hormone secreted by the parathyroid glands, r egulating the serum calcium through its effects on bone, kidney, and intestine.
Thus, this is the main difference between calcitonin and parathyroid hormone. Moreover, the thyroid gland secretes calcitonin while parathyroid gland secretes parathyroid hormone.
The secretion of calcitonin is stimulated by the elevated calcium levels in the blood while the secretion of parathyroid hormone is stimulated by low calcium levels in the blood. Hence, this is another difference between calcitonin and parathyroid hormone. Calcitonin reduces the calcium concentration in the blood, while parathyroid hormone increases the calcium concentration in the blood. Furthermore, the calcitonin indirectly increases the mineralization and the synthesis of the bone matrix, while the parathyroid hormone increases the formation of osteoclasts, increasing bone resorption.
Low levels of calcitonin lead to osteopenia, while low levels of parathyroid hormone lead to hypothyroidism. High levels of calcitonin lead to hypocalcemia , while high levels of parathyroid hormone lead to hyperthyroidism. Basically, calcitonin is a peptide hormone secreted by the thyroid gland in response to high calcium levels in the blood.
Moreover, it is responsible for reducing the calcium levels in the blood by increasing bone mineralization and the synthesis of bone matrix. Studies on the physiology of the parathyroid glands: calcium and phosphorus studies on a case of idiopathic hypoparathyroidism. Aurbach , G. Isolation of parathyroid hormone after extraction in phenol.
PubMed Google Scholar. Marks , and A. Parathyroid hormone, calcitonin, and the calciferols. In: Textbook of Endocrinology 7th edition , edited by J.
Wilson and D. Philadelphia, PA: Saunders, Google Scholar. Barnicot , N. The local action of parathyroid and other tissues on bone in intracerebral grafts. Bliss , M. The Discovery of Insulin. Chicago, IL: Univ. CrossRef Google Scholar.
Brewer , H. Keutmann , J. Potts , JR. Reisfeld , R. Schleuter , and P. Isolation and chemical properties of porcine thyrocalcitonin. Bussolati , G. Chambers , D. Dunham , J. Zanelli , J.
Parsons , L. Bitensky , and J. A sensitive bioassay of parathyroid hormone in plasma. Collip , J. The parathyroid glands. Harvey Lect. Cooper , C. Schwesinger , A. Mahgoub , and D. Thyrocalcitonin: stimulation of secretion by pentagastrin.
Science Wash. DC —, Copp , D. Cameron , B. Cheney , A. Davidson , and K. Evidence for calcitonin—a new hormone from the parathyroid that lowers blood calcium. Endocrinology —, Cockcroft , and Y. Calcitonin from ultimo-branchial glands of dogfish and chickens. Foster , G. Baghdiantz , M. Kumar , E. Slack , H.
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