Effect of the GnRH stimulation test on canine prostatic specific esterase (CPSE).

The gonadotropin releasing hormone (GnRH) stimulation test is used to investigate testicular production of testosterone (T) when performing a breeding soundness examination. In male dogs with fertility problems the prostate should also be investigated as prostatic conditions may frequently lower semen quality. Serum concentrations of canine prostatic specific esterase (CPSE) increase in dogs with benign prostatic hyperplasia (BPH). When performing a breeding soundness examination in a male dog GnRH administration is frequently done at the beginning of the process and then both T and CPSE are assayed on the same serum sample collected one hour following the GnRH injection. The aim of this study was to assess whether or not the administration of GnRH may alter CPSE concentrations in dogs with a healthy prostate. Twenty-eight client-owned intact adult male dogs were included in the study. Following a 7-day sexual rest all male dogs underwent a clinical examination and an ultrasonographic exam of the prostatic gland. Prostatic size and parenchyma of every tested dog was evaluated by ultrasonography to assess prostatic conditions. Two different GnRH stimulation protocols were used, A = gonadorelin 50 μg/dog SC (n=15) and B = buserelin 0.12 μg/kg IV (n=13). T and CPSE concentrations were measured before and one hour after GnRH administration by a laser-induced fluorescence analysis. Buserelin and gonadorelin were equally effective in causing a significant increase in serum T concentrations in the post GnRH sample. When considering the 28 dogs together CPSE concentrations did not change following the stimulation test with either GnRH compound; however, in 4/28 cases the post GnRH value was markedly increased to values compatible with a diagnosis of BPH. There was no difference in the action of buserelin or gonadorelin in causing an increase in serum T concentrations. CPSE secretion was increased in approximately 15% of dogs treated with either buserelin or gonadorelin. Therefore, whenever performing diagnostic testing in intact male dogs, CPSE should not be assayed on a post-GnRH serum sample.