Secreting active thyroid follicles are lined by

Thyroid follicles lining epithelium depends upon the secretion of thyroxine More the secretion,more the endoplasmic reticulum,more the height of the cell, becoming columnar. Resting follicle - Squamous Normal follicle - Cuboidal Active follicle - Columnar Ref: IB Singh textbook of histology 6e pg 325.