Final answer:
Progesterone is produced by the corpus luteum in response to a surge of LH, and is vital for pregnancy establishment and regulation of the menstrual cycle. Without it, the uterine lining wouldn't prepare properly for implantation and the regulation of other fertility hormones would be disrupted.
Step-by-step explanation:
Progesterone is produced in response to a surge of luteinizing hormone (LH) during the ovarian cycle. When LH levels surge, they promote the transformation of granulosa and theca cells within the collapsed follicle into a new endocrine structure known as the corpus luteum. This process, called luteinization, results in the corpus luteum producing large amounts of progesterone, which is essential for the establishment and maintenance of pregnancy. Additionally, progesterone induces a negative feedback loop that inhibits the secretion of gonadotropin-releasing hormone (GnRH), LH, and follicle-stimulating hormone (FSH), preventing the development of new dominant follicles during this period.
If the corpus luteum did not produce increasing amounts of progesterone, this would disrupt the secretory phase of the menstrual cycle where the uterine lining prepares for potential implantation of a fertilized egg. Progesterone plays a crucial role in making the vaginal environment hospitable to sperm and in maintaining the uterine lining. Without sufficient progesterone, the endometrium would not be properly prepared for implantation, possibly leading to a failure in establishing a pregnancy. Additionally, without the negative feedback from progesterone, FSH and LH levels would not be properly regulated, which could lead to abnormal development of follicles in the ovaries.