luteinized

Luteinized is an adjective used in biology and medicine to describe tissue that has undergone luteinization, the transformation of certain ovarian follicle cells into luteal cells as part of corpus luteum development.

In the normal ovarian cycle, after ovulation the ruptured follicle transforms into the corpus luteum. This process involves luteinization, in which granulosa cells (the granulosa-lutein cells) and theca interna cells (the theca-lutein cells) differentiate into steroid-secreting luteal cells. The resulting luteal tissue primarily produces progesterone, with smaller amounts of estrogen, supporting the luteal phase of the cycle and the early uterine environment for potential implantation. If fertilization occurs, human chorionic gonadotropin (hCG) rescues the corpus luteum to maintain progesterone production; if pregnancy does not occur, the corpus luteum regresses and becomes a scar called the corpus albicans.

Histologically, luteinized cells are typically polygonal with abundant eosinophilic cytoplasm rich in lipid droplets, giving a yellowish appearance to the tissue in gross sections (hence the name luteinized). They are highly vascularized and contain steroidogenic enzymes that drive progesterone synthesis.

Clinically, luteinization is a normal and essential part of the menstrual cycle and early pregnancy maintenance. Abnormal or extreme luteinization can be observed in certain ovarian tumors or in response to assisted reproductive technologies, where luteinized stromal or lutein-like cells may be described.