Plasma Concentrations of Testosterone, Luteinizing Hormone, and Estrone Sulfate in Stallions Following Hemicastration

Hemicastration is a veterinary surgical procedure in stallions and may be needed for removal of a diseased testicle. The effects of hemicastration on the neuroendocrine system and the hormonal response of the remaining testicle are unclear. In this study, blood plasma concentrations of testosterone, luteinizing hormone, and estrone sulfate were assessed following hemicastration. Miniature stallions (n=8) were used in this study and blood was drawn 7 d prior to hemicastration, and 12 h, 48 h, 14 d, 30 d, and 90 d post hemicastration. Blood samples from all stallions were drawn every 15 min (0, 15, 30, 45, 60 min) for 1 h each sampling period. Plasma was analyzed by RIA for concentrations of testosterone, luteinizing hormone, and estrone sulfate. Compared to pre-surgerical concentrations, plasma luteinizing hormone at 12 h, 48 h, 14 d and 60 d were greater (P < 0.05). Compared to 12 h, plasma testosterone values at 48 h, 14 d, and 60 d were higher (P < 0.05). Compared to pre-hemicastration values, plasma concentrations of estrone sulfate were lower (P < 0.05) at all time periods, but tended to increase up to 60 d. After 30 d, stallions were housed together rather than individually creating a harem group. Luteinizing hormone and testosterone values increased dramatically compared to previous time periods following the housing modification. These results provide insight to better understand the hormonal profiles and compensatory response of the remaining testicle following hemicastration.