The Thyroid Follicles - T4 / T3 thyroid hormone production site
The functional units of the thyroid gland are spherical follicles - balls of follicular cells with hollow centers - each follicle consists of:
– Thyroid follicular cells (simple cuboidal type, aka. thyroid epithelial cells, follicular epithelial cells, thyrocytes); form the outside boundary . . .
– Filled with a viscous material called colloid - which contains mostly glycoprotein thyroglobulin (Tg) molecules, that provide:
✔ The glycoprotein backbone for synthesis and storage of thyroid hormones
✔ A convenient depot for iodine storage and retrieval - when external iodine availability is scarce or erratic.