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Parafollicular cells, also called C cells, are neuroendocrine cells in the thyroid. They are called C cells because the primary function of these cells is to secrete calcitonin. [1] They are located adjacent to the thyroid follicles and reside in the connective tissue. These cells are large and have a pale stain compared with the follicular cells.
Calcitonin is a 32 amino acid peptide hormone secreted by parafollicular cells (also known as C cells) of the thyroid (or endostyle) in humans and other chordates [5] in the ultimopharyngeal body. [6] It acts to reduce blood calcium (Ca 2+), opposing the effects of parathyroid hormone (PTH). [7]
At the microscopic level, there are three primary features of the thyroid—thyroid follicles, thyroid follicular cells, and parafollicular cells, first discovered by Geoffery Websterson in 1664. [14] Follicles. Thyroid follicles are small spherical groupings of cells 0.02–0.9mm in diameter that play the main role in thyroid function. [4]
Calcitonin-producing parafollicular cells are also found along the basement membrane of the thyroid follicle, interspersed between follicular cells; and in spaces between the spherical follicles. Parafollicular cells can be distinguished from follicular cells based on their lighter staining cytoplasm using H&E.
The thyroid secretes thyroxine, the pituitary secretes growth hormone, the pineal secretes melatonin, the testis secretes testosterone, and the ovaries secrete estrogen and progesterone. [ 2 ] Glands that signal each other in sequence are often referred to as an axis, such as the hypothalamic–pituitary–adrenal axis .
It develops into the parafollicular cells of the thyroid. [2] The cells that give rise to the parafollicular cells are derivatives of endoderm . [ 3 ] Endoderm cells migrate and associate with the ultimopharyngeal body during development.
Medullary thyroid cancer is a form of thyroid carcinoma which originates from the parafollicular cells (C cells), which produce the hormone calcitonin. [1] Medullary tumors are the third most common of all thyroid cancers and together make up about 3% of all thyroid cancer cases. [2] MTC was first characterized in 1959. [3]
The endocrine glands belong to the body's control system. The hormones which they produce help to regulate the functions of cells and tissues throughout the body. Endocrine organs are activated to release their hormones by humoral, neural, or hormonal stimuli. Negative feedback is important in regulating hormone levels in the blood.