Thyroid follicular cell

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Thyroid follicular cell
thyroxine (T4) and triiodothyronine (T3).
Anatomical terms of microanatomy]

Thyroid follicular cells (also called thyroid epithelial cells or thyrocytes

cuboidal epithelium
that makes up the outer structure of the almost spherical thyroid follicle.



Thyroid follicular cells form a simple

follicular lumen. The basolateral membrane of follicular cells contains thyrotropin receptors which bind to thyroid-stimulating hormone
(TSH) found circulating in the blood.

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.


Their embryologic origin is from a median endodermal mass in the region of the tongue (foramen cecum) in contrast to parafollicular cells which arise from the 4th pharyngeal pouch.


Thyroid hormone synthesis.[2]

Follicular cells take up

thyroperoxidase from amino acids and secrete these into the thyroid follicles together with iodide. The follicular cells subsequently take up iodinated thyroglobulin from the follicles by endocytosis, extract thyroid hormones from it with the help of proteases
and subsequently release thyroid hormones into the blood.

These thyroid hormones are transported throughout the body where they control metabolism (which is the conversion of oxygen and carbohydrates to energy). Every cell in the body depends upon thyroid hormones for regulation of their metabolism. The normal thyroid gland produces about 80% T4 and about 20% T3, however, T3 is about four times as potent as T4.

Iodide transport

The transport of iodide into follicular cells is vital for the synthesis of the

sodium-iodide symporter.[3] At the apical membrane iodide is secreted into the colloid by the chloride/iodide transporter pendrin

See also


  1. ^ Mescher, Anthony L. Junqueira's Basic Histology, 14th edition. Lange. p. 430.
  2. .
  3. .

External links