Endocrine diagnostics in subfertile stallions

Diagnostic endocrine testing

Diagnostic endocrine testing in stallions has had limited application in veterinary practice other than for diagnosis of suspected cryptorchidism in previously castrated stallions. The lack of widely available standardised assays for equine gonadotropins has hindered their diagnostic use in subfertile stallions [1], and the relative paucity of information related to diagnostic interpretation of endocrine values has made the clinical application of reproductive endocrinology difficult. Endocrine concentrations in stallions must be interpreted in terms of the stallion’s age, and the season of the year because both these variables have significant effects on luteinising hormone (LH) and testosterone concentrations in plasma [2]. Sexual stimulation can also cause significant increases in peripheral concentrations of testosterone and should be avoided in obtaining baseline determinations [3]. Because secretion of the gonadotropins in the stallion is pulsatile, samples taken over the course of 3 days may be more representative than a single sample. Furthermore, there appears to be a diurnal variation in hormone concentrations so that concentrations are highest around mid-day, and some authors suggest that endocrine sampling should be conducted prior to 09.00 h. [4]. […]