Which hormone stimulates the growth of the endometrium?

Estrogen is the hormone primarily responsible for stimulating the growth of the endometrium, which is the inner lining of the uterus. During the menstrual cycle, particularly in the follicular phase, rising levels of estrogen, produced by the developing follicles in the ovaries, lead to the proliferation of the endometrial cells. This prepares the uterine lining for potential implantation of a fertilized egg.

In contrast, progesterone plays a different, albeit supportive, role in the menstrual cycle. After ovulation, during the luteal phase, progesterone helps to stabilize and maintain the thickened endometrial lining but does not stimulate its initial growth. Other hormones such as FSH and LH are involved in regulating the ovarian cycle, including follicle development and ovulation, but they do not directly influence the growth of the endometrium. Therefore, estrogen is indeed the key hormone for stimulating endometrial growth.