Secreting active thyroid follicles are lined by which type of epithelium:

Secreting active thyroid follicles are lined by columnar type of epithelium. Thyroid follicle epithelial lining depends on activity of cells involved in secretion of thyroxine. The more the secretion, the more is endoplasmic reticulum content, the more is the height of the cell - tendency to become columnar. Scanty (resting follicle)- simple squamous Medium (normal follicle)- simple cuboidal High (active follicle)- simple columnar(secreting epithelium) Note: Normally a thyroid follicle is mostly lined by cuboidal epithelium (central spehrical nucleus, with height of the cell equal to breath).