What is the primary function of progesterone produced by the corpus luteum?

The primary function of progesterone produced by the corpus luteum is to thicken the endometrium. After ovulation, the corpus luteum forms from the ruptured follicle and secretes progesterone. This hormone plays a crucial role in preparing the endometrium for potential implantation of a fertilized egg. Progesterone promotes the development of a secretory lining in the uterus, making it more receptive to an embryo. This thickened endometrial lining is essential for supporting early pregnancy if fertilization occurs.

In the context of the other choices, while progesterone does support menstruation by maintaining the endometrial lining until pregnancy is confirmed, its direct role is not about triggering menstruation itself. Instead, if pregnancy does not occur, the decline in progesterone levels leads to menstruation. Triggering ovulation is primarily the role of luteinizing hormone, while follicle development is primarily stimulated by follicle-stimulating hormone. Therefore, the connection of progesterone to the endometrial thickening highlights its critical role in preparing the uterus for possible pregnancy.