Calcitonin Thyrocalcitonin

The main role of the human thyroid gland is production of thyroid hormones (iodinated amino acids), essential for adequate growth, development, and energy metaboHsm (1 6). Thyroid underfunction is an occurrence that can be treated successfully with thyroid preparations. In addition, the thyroid secretes calcitonin (also known as thyrocalcitonin), a polypeptide that lowers excessively high calcium blood levels. Thyroid hyperfunction, another important clinical entity, can be corrected by treatment with a variety of substances known as antithyroid dmgs. 

Several years ago, it was discovered that the thyroid gland was also the source of a hypocalcemic hormone having effects in general opposition to those of the parathyroid hormone. This hormone is produced in mammals by the parafollicular C-ceUs and in other vertebrates by the ultimobrachial bodies (45). Originally called thyrocalcitonin, it is now referred to as calcitonin (CT). 

Calcitonin and Thyrocalcitonin David Webster and Samuel C. Frazer... 

Bouvet JP. Traitement de la maladie de Paget par la thyro-calcitonine de sanmon. Etude cooperative en double insu. [Treatment of Paget s disease with salmon thyrocalcitonin. Cooperative double-blind stndy.] Nonv Presse Med 1976 6(17) 1447-50. 

Thyrer thyrotrophin-releasing hormone, thyreotrophic hormone thyrotrophin. thyrocalcitonin calcitonin. a thyrocalcitonin calcitonin (pork), thyroglobulin [inn, usan] is obtained from thyroid glands of Sus scrota (hog), and contains >0.7% total iodine. It acts as a THYROID HORMONE, and was formerly used in the treatment of hypothyroidism. 

Several animal species have been used in the biological assay of calcium-lowering hormones. For reasons of size, the rat is most commonly used, although mice have been claimed to be more responsive to human thyrocalcitonin preparations (S2). For studies of the course of thyro-calcitonin action in which serial blood samples were required, both pigs (C5) and goats (F4) have been used. For assessment of the potency of hoimone preparations, bioassay in rats is in general satisfactory. 

Arnaud and Littledyke (A5) and Hargis et al. (HI) overcame the problem of antigenicity by conjugating relatively pure porcine thyro-calcitonin to rabbit albumin before injection, and claim that the antisera obtained were specific to thyrocalcitonin, judged by gel diffusion and immunoelectrophoresis results. The former workers have briefly described the use of this antiserum in a radioimmunoassay procedure similar to that devised by Berson et al. for parathormone (B4). They claim that the technique will detect 0.5 ng of thyrocalcitonin/ml of serum. These workers found no difference in the immunological behavior of human and porcine hormone, and quote a normal range of 30-85 ng/ml in human plasma. In animal studies, elevated values were found in older animals and in response to hypercalcemia. 

The known effects of thyrocalcitonin are primarily in bone. Removal of the gut had no effect on the hypocalcemic effect of calcitonin (A6), and neither did nephrectomy (H8). No change in soft tissue calcium content was seen in soft tissues to explain the hypocalcemia (Kl). Calcitonin apparently inhibits bone resorption and thereby decreases calcium entry into the blood. Calcitonin prevents the release of calcium from cultured bone (A5, FIO). In vivo, the release of Ca from prelabeled bone is decreased by calcitonin (Jl). The bone arteriovenous difference in calcium levels is increased by calcitonin (M3). The mode of action of calcitonin is unknown. Calcitonin does not inhibit parathormone (A6, H7, T3), nor is its effect apparently mediated through RNA synthesis (T3). 

When thyrocalcitonin was given to patients with hypercalcemia due to a variety of causes, serum calcium levels fell (B9, F7, HI). The magnitude of the effect was related to the degree of calcium elevation (HI). It would appear that the use of calcitonin for treatment of acute hypercalcemia is not warranted at this time. Studies of the long-term use of thyrocalcitonin in diseases such as osteoporosis have not yet been reported. 

Hormones have recently been discovered that are likely to act on bone by either preventing resorption or facilitating deposition of calcium [29-31]. One of these hormones was found in the parathyroid gland (calcitonin), the other, in the thyroid gland (thyrocalcitonin). Thyro-calcitonin, which has been purified from pig thyroids, is a polypetide hormone with a molecular weight of 3,000 and composed of 32 amino acids (see Fig. 5-13). The intact sequence is indispensable for activity. The amino terminal segment of the molecule contains an intrachain disulfide bridge. 

Calcitonin is active in nephrectomized and parathy-roidectomized animals, indicating that the hormone does not act through the kidney or the parathyroid. Thyrocalcitonin causes hypocalcemia even in rats fed a low-calcium diet. Consequently, the hormone does riot seem to influence intestinal absorption of calcium. Calcitonin facilitates calcium retention in bone cultures. It is likely that the hormone acts by interfering with calcium resorption in bone, but the exact mechanism by which the interference takes place is not known. 

The plasma phosphorus level (which generally falls within the range of 2.5 to 4.5 mg per 100 ml in adults—higher in children), along with calcium. Is regulated by the parathyroid hormone and thyrocalcitonin (calcitonin) and is inversely related to the blood calcium level. 

Copp, D.H. (1968). "Development of the calcitonin concept - a decade in perspective." In Calcitonin Symposium on Thyrocalcitonin and the C Cells. Edited by S. Taylor, London, Heinemann Medical Books, in press. 

Inhalable co-spray dried powders of salmon calcitonin-loaded chitosan nanoparticles with mannitol have been prepared and analyzed. Salmon calcitonin or Calcitonin (also known as thyrocalcitonin) is a 32-amino acid linear polypeptide hormone that is produced in humans primarily by the parafollicular cells (also known as C-cells) of the thyroid, and in many other animals in the ultimobranchial body. It acts to reduce blood calcium (Ca ), opposing the effects of parathyroid hormone (PTH) [118]. The... 

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