the glandular-epithelial cells that form the outer layer of the corpus luteum.
Lutein cells develop from cells of the Graafian follicle, usually after it sheds the oocyte (ovulation). The protoplasm of lutein cells contains a lipid pigment called lutein (one of the lipochromes). Lutein cells elaborate the hormone progesterone. They break down with the involution of the corpus luteum during the second half of pregnancy, before estrus, and before menstruation.