Clinical Tests to Predict the Success of Assisted Reproductive Techniques

Today, it is evident that vitamin D has more widespread effects than the classical actions related to bone mineralization and calcium homeostasis. Vitamin D deficiency results in impaired reproductive performance in various species of animals, and recently the investigators have shown that the Vitamin D receptor (VDR), activating (CYP2R1, CYP27A1, CYP27B1) and inactivating (CYP24A1) enzymes are expressed in the human testis, epididymis, seminal vesicle, prostate and spermatozoa. Functional studies showed that activated vitamin D increases intracellular calcium and sperm motility in mature spermatozoa, and hence may be important not only for spermatogenesis but also for sperm function. Any test that might assist in guiding the treatment of the infertile couple would be beneficial both for most infertile couples and the society in general. The fact that vitamin D may play a role for human semen quality are now being tested clinically. If vitamin D supplementation proves efficient this opens for the first time for a causal, safe and cheap treatment of at least some cases of "idiopathic" impaired semen quality. This may also have consequences in the in vitro setting as activated vitamin D may be used to select high quality sperm during assisted reproductive techniques. The presence of the vitamin D receptor and vitamin D metabolizing enzyme CYP24A1 in particular is able to discriminate spermatozoa from normal and infertile men. CYP24A1 is expressed at the annulus of normal sperm, but it is virtually absent from spermatozoa from infertile men. This indicates that CYP24A1 expression may assist in predicting the chance of success by using insemination (IUI), IVF or ICSI. CYP24A1 expression is induced by activated vitamin D, which indicates that other VDR activated genes also may serve as positive predictive markers of fertility. In addition, vitamin D metabolites and other factors in the female reproductive tract will be measured to determine if they alone or in combinatio