Britannica Sources used in this answer

What does thyroid colloid contain?

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 colloid is a fluid substance stored within the follicles of the thyroid gland. Its primary component is thyroglobulin, an iodine-containing glycoprotein that serves as a precursor to thyroid hormones.123

This storage arrangement acts as a reserve for thyroxine and triiodothyronine. When the body requires these hormones, thyroid cells reabsorb the colloid, and enzymes break down the thyroglobulin to release the active hormones into the bloodstream.12