Theca lutein cells are also known as small luteal cells.

Theca lutein cells secrete androgens and progesterone.

However, after ovulation the granulosa cells turn into granulosa lutein cells that produce progesterone.

After rupture of the mature ovarian follicle, the theca interna cells differentiate into the theca lutein cells of the corpus luteum.

In the mature CL, granulosa lutein cells showed diminution of cytoplasmic LHR immunoreactivity and strong surface staining (Fig.

For example, a lower plating density makes granulosa cells exhibit estrogen production, while a higher plating density makes them appear as progesterone-producing theca lutein cells.

FS mRNA remained undetectable in the CL until P 2000 h when high expression was induced in a subset of lutein cells (Fig.

Like the previous theca cells, the theca lutein cells lack the aromatase enzyme that is necessary to produce estrogen, so they can only perform steroidogenesis until formation of androgens.

Early luteal development (fresh CL) was associated with very strong cytoplasmic LHR immunostaining of granulosa lutein cells migrating into the follicular cavity (gl, Fig.

Regression of luteal tissue (CL investigated during the follicular phase) showed residual staining of theca-lutein cells and no staining of regressing granulosa lutein cells (Fig.

In porcine ovaries, LHR expression was detected in granulosa and theca cells of preovulatory follicles, but not in granulosa lutein cells of the mature CL [ 27 ] .

In other words, selective pick up of CG through the surface LHR expression in granulosa lutein cells during the luteal phase after conception appears not to be required if the circulating CG is very high.

The granulosa lutein cells do have aromatase, and use it to produce estrogens, using the androgens previously synthesized by the theca lutein cells, as the granulosa lutein cells in themselves do not have the 17α-hydroxylase or 17,20 lyase to produce androgens.