<prompt> Secreting active thyroid follicles are lined byColumnarCuboidalSquamousPseudo stratified squamous  <response>: 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. 