Parafollicular cell

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The parafollicular cells are cells in the thyroid gland in mammals. They are called parafollicular because they are located individually or in groups in the connective tissue of the thyroid gland between or next to ( syn. Para ) the thyroid follicles. The main function of the parafollicular cells is the production of the hormone calcitonin and they are accordingly referred to as C cells ( C for calcitonin). Phylogenetically they derive from the ultimobranchial bodies ( Glandula ultimobranchialis), which exist as separate organs in other vertebrates.

Calcitonin engages the Calcium - Phosphate - metabolism one in which it is the calcium concentration by inhibition of osteoclasts and reduced calcium intake in the digestive tract lowers. The release of calcitonin is regulated via G-protein- coupled calcium receptors located in the plasma membrane of the parafollicular cells . They are stimulated by a high calcium concentration and cause a signal cascade to depolarize and lower the pH value ( acidification ) within the calcitonin-containing vesicles , which causes the vesicle contents to be released and thus the endocrine release of the calcitonin.

In addition, the parafollicular cells form a whole range of other messenger substances ( mediators ) such as serotonin , " calcitonin gene-related peptides " (CGRP) and somatostatin , the function of which in the thyroid gland has largely not yet been reliably clarified. It is assumed that some mediators have a regulatory effect on the formation of the thyroid hormones triiodothyronine (T 3 ) and thyroxine (T 4 ) in the follicular epithelial cells of the thyroid gland.

The parafollicular cells are the APUD system (APUD = A mine P recursor U ptake and D ecarboxylation) allocated. Like all APUD cells, they are descendants of the neural crest .

The malignant tumor that originates from the C cells is medullary thyroid carcinoma . This tumor is common in multiple endocrine neoplasia of the MEN 2 type.

further reading

  • EC Baber: Contributions to the minute anatomy of the thyroid gland of the dog. In: Phil Trans R Soc. 166, 1876, pp. 557-568 ( full text )

swell

  • H. Leonhardt: Histology, cytology and microanatomy of humans. 8th edition. Thieme Verlag , 1990, ISBN 3-13-371508-9 , p. 387 ff.
  • KP Liu et al .: Calcium receptor-induced serotonin secretion by parafollicular cells: role of phosphatidylinositol 3-kinase-dependent signal transduction pathways. In: J Neurosci. 23 (6), 2003 Mar 15, pp. 2049-2057. PMID 12657663