Which hormone stimulates the lining of the womb to prepare for pregnancy?

Oestrogen is the hormone that plays a critical role in preparing the lining of the womb, or endometrium, for pregnancy. This preparation occurs during the menstrual cycle, specifically in the follicular phase, leading up to ovulation. As the ovaries produce oestrogen, it stimulates the thickening of the uterine lining, making it more receptive to a fertilized egg.

Once an egg is released during ovulation, oestrogen works in conjunction with progesterone (which is also crucial for maintaining the uterine lining post-ovulation) to ensure that the endometrium is well-prepared for potential implantation. If fertilization does not occur, levels of oestrogen drop, leading to the shedding of the uterine lining during menstruation.

Other hormones mentioned in the options, while important in the reproductive cycle, do not directly cause the uterine lining to prepare for pregnancy in the same manner as oestrogen. For instance, testosterone primarily influences male characteristics and reproductive functions, LH (luteinizing hormone) primarily triggers ovulation, and FSH (follicle-stimulating hormone) is crucial for the development of ovarian follicles but does not directly affect the preparation of the uterine lining.