<prompt> Answer this question truthfullyWhat is the substance in which iodinated thyroglobulin is stored in the follicular lumen until the thyroid gland is stimulated to secrete thyroid hormones?  <response>: <reason> After iodinated thyroglobulin is synthesized, it is stored in the follicular lumen as colloid until the thyroid gland is stimulated to secrete thyroid hormones. 