140 Endocrine Profiling in Prepubertal Stallions with Abnormal Testicular Development

Abstract

The use of anti-Müllerian hormone (AMH) as a biomarker for assessment of male gonadal activity has become increasingly widespread. Aberrant AMH concentration successfully detects cryptorchids or pathologic testes in postpubertal stallions, but the ability to use AMH to identify stallions with testicular pathologies during their prepubertal life has not been analysed so far. The objectives of this work were to (1) assess AMH, testosterone, LH, and FSH dynamics in male horses with or without testicular pathologies during the first year of life; and (2) find a reliable diagnostic approach that would enable the identification of animals that will develop abnormal testes at an early stage. Warmblood colts (n = 16) born from February to May on the same stud farm were used. Blood samples for hormone determinations were collected from birth onwards every 4 weeks until the age of 1 year. At 2 years, testicular development was assessed, total testicular volume calculated. and a blood sample collected. Concentrations of AMH, testosterone, LH, and FSH were determined in all samples; AMH (AL-115, Ansh Laboratories, Webster, TX, USA) and testosterone (DE1559, Demeditec, Kiel-Wellsee, Germany) concentrations were determined by ELISA, whereas LH and FSH concentrations were determined by radioimmunoassay. Statistical analysis (SPSS Statistics 24; IBM/SPSS, Armonk, NY, USA) was performed by ANOVA using a general linear model for repeated measures. In 2 stallions, unilateral cryptorchism, and in other 4 stallions, subnormal total testicular volume (<mean minus SD) were diagnosed at 2 years. Concentrations of AMH, testosterone, and FSH changed over time (P < 0.001) but were similar (P > 0.05) within the first year of life irrespective of testicular morphology and location. Concentration of LH at birth was lower (P = 0.05) in stallions with abnormal testes (0.3 ± 0.2 ng mL⁻¹) than in controls (0.6 ± 0.2 ng mL⁻¹), but did not differ thereafter. At 2 years of age, AMH concentration was higher (P < 0.01) in stallions with abnormal testes (39.7 ± 12.7 ng mL⁻¹) than in controls (8.0 ± 0.2 ng mL⁻¹), but no group differences with regard to LH, FSH, and testosterone existed. There was a low but significant negative correlation between AMH and FSH (P < 0.001, r = –0.24), as well as between AMH and LH (P < 0.05, r = –0.15). Also, testosterone concentration was positively correlated with FSH (P < 0.05, r = 0.18) and LH (P < 0.05, r = 0.16) concentrations. In conclusion, AMH determination can be reliably used from 2 years onwards to identify stallions with abnormal testicular development, but it is inconclusive before puberty. We concluded that LH secretion in the perinatal period is involved in testicular development and descent in the horse.