Function of the Pituitary-Ovarian Axis

The most useful markers for a successful outcome of assisted reproduction are those that can be assessed before the treatment begins. The following tests are therefore less useful from a clinical point of view. However, sometimes a stimulation or challenge test can give more detailed information about the functioning of the endocrine system of a subject, or can predict pregnancy more precisely than baseline tests. 

In order to establish a functional test for fertility potential, Navot et al. (N3) have described the clomiphene citrate challenge test (CCCT). In short, FSH is measured on cycle day 3 and on cycle day 10, while on cycle days 5-9, 100 mg of clomiphene citrate is administered daily. When response FSH is high, ovarian reserve is considered diminished. The reason for the overshoot of FSH in women with diminished ovarian reserve is claimed to be a reduced capacity to secrete inhibin in these women (H9, N3). 

The CCCT can be interpreted in several ways as originally described, the test is abnormal if the second FSH level is high, but others consider the test also abnormal if either the first or the second FSH level is high, if the second FSH level is higher than the first one, or if the sum of basal and stimulated FSH is above a certain level. Finally, estradiol concentration can be taken into account in the interpretation of 

Stimulated estradiol levels after clomiphene citrate stimulation are lower in older patients with regular cycles compared to younger women (G2), but they are not correlated with any outcome parameter in IVF (SI2). Therefore, although the response of estradiol in a CCCT might give some insight into the function of the ovaries, it is of no prognostic value in IVF. 

The CCCT is able to detect those patients with normal basal FSH levels who have a high risk of a poor response in assisted reproduction. 

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