Blood steroid concentrations in domestic Mongolian horses

Traditionally, analysis of blood cortisol alone has been used to evaluate adrenal function. Currently, multisteroid analyses are considered more informative than analysis of a single hormone to assess adrenal function. The objective of the present research was to create a database for steroid reference values for domestic Mongolian horses. Seven adrenal steroid levels were determined in the blood of 18 colts, 34 stallions, 25 geldings, 17 fillies, and 29 mares. Results were as follows (lowest and highest group median, in nanograms per milliliter): progesterone: <0.030 (fillies), 4.30 (mares), and 0.070 (all horses); 17-OH-progesterone: 0.070 (colts), 0.520 (mares), and 0.110 (all horses); androstenedione: 0.101 (colts), 0.256 (stallions), and 0.181 (all horses); testosterone: <0.040 (mares, stallions, and fillies), 0.040 (geldings and colts), and <0.40 (all horses); estradiol: 0.066 (stallions), 0.093 (fillies), and 0.085 (all horses); cortisol: 23.040 (colts), 70.210 (geldings), and 50.770 (all horses); and aldosterone: 0.018 (colts), 0.297 (geldings), and 0.191 (all horses). Overall medians indicate that cortisol (98.70%) is the predominant steroid, followed by aldosterone (0.37%), androstenedione (0.35%), 17-OH-progesterone (0.21%), estradiol (0.17%), progesterone (0.14%), and testosterone (0.06%). This information provides adrenal and gonadal steroid reference concentrations to assist in physiological characterization and diagnosis of endocrine disorders in domestic Mongolian horses.