What are thyroid follicles?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Detailed anatomical illustration of the human thyroid gland and surrounding structures, showing the right and left lobes, isthmus, nearby arteries, veins, nerves, lymph nodes, and cartilage in the neck. — thyroid gland Human thyroid gland.

Thyroid follicles are small, globular sacs that make up the lobes and isthmus of the thyroid gland.1

These structures are lined with follicular cells and contain a fluid called colloid. The colloid serves as a storage site for thyroglobulin, a prohormone. The follicular cells play a critical role in the synthesis and release of thyroid hormones; they contain the enzymes necessary to produce thyroglobulin and to extract thyroxine (T4) and triiodothyronine (T3) from it when the body requires them. Once processed, these hormones are released into the circulatory system.1