The central lumens of thyroid follicles are filled with colloid, which consists of the protein thyroglobulin, a molecule that binds and stores thyroid hormone.
Thyroglobulin is a protein produced primarily by the thryroid gland. The thyroid gland is mainly made up of tiny, round shaped structures called follicles that produce and store thyroglobulin. Thyroglobulin acts as a substrate for the synthesis of the hormones (thyroxine and triiodothyronine) and also the storage of the inactive forms of thyroid hormone and iodine. Thyroxine and triiodothyronine assist in the regulation of the utilization of energy by the body.
