Parafollicular cell (C cell)
Cellula parafollicularis
Also known as: C cell, clear cell
Pale neuroendocrine cells scattered between and within thyroid follicles that secrete calcitonin in response to high blood calcium; they give rise to medullary thyroid carcinoma.
Overview
C cells are larger and paler than follicular cells, lie singly or in small clusters inside the follicular basal lamina (but do not reach the colloid) or in the interstitium, and are most numerous in the upper and middle thirds of the lateral lobes. They derive from neural crest cells carried into the thyroid by the ultimobranchial body (4th/5th pharyngeal pouch complex) and belong to the diffuse neuroendocrine system, containing granules of calcitonin, calcitonin gene-related peptide and chromogranin.
They express the calcium-sensing receptor: a rise in plasma Ca²⁺ increases calcitonin release. Gastrin and pentagastrin also stimulate them.
- Location
Thyroid gland, between follicular cells and in the interfollicular stroma, concentrated in the upper lateral lobes.
Anatomy
- Histology
Pale-staining cytoplasm on H&E; calcitonin-positive on immunohistochemistry; electron-dense secretory granules.
- Development
Neural crest via the ultimobranchial body.
Function
- Secrete calcitonin, which inhibits osteoclastic bone resorption and lowers plasma calcium.
Clinical significance
Medullary thyroid carcinoma
Malignancy of C cells (≈2–5 % of thyroid cancers); ≈25 % hereditary (MEN2A, MEN2B, familial MTC — germline RET mutations). Secretes calcitonin (tumour marker, amyloid stroma derived from calcitonin) and CEA; may cause diarrhoea and flushing. Hypocalcaemia does not occur despite very high calcitonin — evidence of its small role in adult calcium balance.
Compiled from standard anatomy and physiology references — see the Endocrine System sources. For education only; not medical advice.