Human Reproduction Problem Set

Problem 5: Female reproductive cycle

Tutorial to help answer the question

In a "typical" 28 day female reproductive cycle, on which day following the beginning of the menstrual period is the level of luteinizing hormone most likely to be highest?


Reproductive cycle

As we saw in problem 4, it is the interaction of the gonadotropic hormones and the ovarian hormones that controls the reproductive cycle.
The first 12 days
For the first 12 days of the menstrual cycle, estrogen has a negative effect on the production of gonadotropins.

Following these 12 days the negative effect changes to a positive effect on the production of gonadotropic hormones.

This results in a small increase of follicle stimulating hormone (FSH), but a large increase of luteinizing hormone (LH.)

This sudden increase of LH causes the mature follicle to release the egg. Following release of the ovum, the ruptured ovarian follicle develops into the corpus luteum.

End of the cycle
The corpus luteum, in turn, secrete estrogen and progesterone. These ovarian hormones are important for the maintenance of the endometrial lining of the uterus where the blastocyst implants itself.

Continued high levels of estrogen and progesterone produce a negative feedback on the secretion of gonadotropins by the anterior pituitary gland.

The Biology Project
University of Arizona
Updated: July 15, 1999
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