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What fluid fills thyroid follicles?

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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.

The thyroid follicles are filled with a fluid known as colloid, which is also referred to as thyrocolloid. This substance contains the prohormone thyroglobulin, which serves as the storage form for thyroid hormones.123