Data-derived reference profiles with corepresentation of progesterone, estradiol, LH, and FSH dynamics during the bovine estrous cycle
Résumé
Subfertility in cows is often associated with alterations in the hormonal patterns involved in the regulation of the estrous cycle. Reference profiles are needed to ground modeling projects aimed at describing these alterations and to develop tools for detecting abnormal dynamics. Various schematic views of LH, FSH, progesterone (P4) and estradiol (E2) patterns have been published but with no clear indication of the extent to which they are derived from real data. The objective of this study was to generate standard profiles for the main reproductive hormones that can be proposed as reliable references to represent the normal dynamics of these hormones over the estrous cycle. A database of hormonal profiles was compiled with 40, 23, 33, and 34 profiles for LH, FSH, E2, and P4, respectively, derived from publications in which changes over time of at least three of these four hormones, including LH, were reported. These profiles were digitalized and standardized over the time throughout the estrous cycle, considering the interval between two successive LH surges to be 21 days. After this standardization on the x-axis, a transformation on the y-axis was performed to center the profiles around their common dynamics. For each hormone, the reference profile was then considered to be the median of the adjusted profiles. Quartiles were reported to account for the time evolution of the variability around each reference profile. The reference profiles obtained showed that the procedure used was satisfactory for extracting the overall changes over time of LH, P4, and E2. Results were less satisfactory for FSH, because of a higher variability observed between the original profiles in our database. The corepresentation of the reference profiles, i.e., when depicted together on the same scale, emphasizes the interplay between these hormones more precisely than most of the schematic views available in literature. These data-derived profiles can be considered to be generic and useful for benchmarking the normal dynamics of gonadotrophins and steroid hormones over the estrous cycle in cow.