OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What hormone is primarily responsible for the thickening of the uterine lining?

1. FSH

2. Progesterone

3. LH

4. Oestrogen

The correct answer is: Oestrogen

The hormone that is primarily responsible for the thickening of the uterine lining is oestrogen. During the menstrual cycle, oestrogen is produced mainly by the developing ovarian follicles and plays a crucial role in stimulating the growth and proliferation of the endometrial tissue in preparation for a potential pregnancy. As oestrogen levels rise, the uterine lining thickens to create a suitable environment for a fertilized egg to implant. While progesterone also contributes to the preparation of the uterine lining, particularly in the later stages of the menstrual cycle, it primarily stabilizes and maintains the lining after it has thickened due to oestrogen. Follicle-stimulating hormone (FSH) is involved in the maturation of ovarian follicles, and luteinizing hormone (LH) triggers ovulation, but neither directly causes the thickening of the endometrium in the way that oestrogen does. Thus, oestrogen is the key hormone in inducing the thickening of the uterine lining during the follicular phase of the menstrual cycle.