Follicular cell

Follicular cells or thyroid epithelial cells are cells in the thyroid gland that produce and secrete thyroid hormones. These cells play a crucial role in the regulation of the body's metabolism, growth, and development.

Structure

Follicular cells are arranged in spheres known as thyroid follicles, which are filled with a substance called colloid. The colloid serves as a reservoir for thyroid hormones. Each follicular cell has a base that is attached to a basement membrane and an apex that faces the colloid-filled lumen of the follicle.

Function

The primary function of follicular cells is the production and secretion of thyroid hormones, specifically thyroxine (T4) and triiodothyronine (T3). These hormones are synthesized from iodine and tyrosine, an amino acid. The process of hormone synthesis involves several steps, including the uptake of iodine by the cells, the iodination of tyrosine, and the coupling of iodinated tyrosines to form T4 and T3.

Follicular cells also produce thyroglobulin, a protein that serves as the precursor for thyroid hormone synthesis. Thyroglobulin is stored in the colloid until it is needed for hormone production.

Clinical significance

Abnormalities in follicular cells can lead to various thyroid disorders. For example, overactivity of these cells can result in hyperthyroidism, a condition characterized by excessive production of thyroid hormones. On the other hand, underactivity can lead to hypothyroidism, which is marked by insufficient hormone production.

Follicular cells can also give rise to thyroid cancer. The most common types of thyroid cancer, papillary thyroid carcinoma and follicular thyroid carcinoma, originate from these cells.

See also

• Thyroid gland
• Thyroid hormones
• Thyroid disorders
• Thyroid cancer