Androgen and oestrogen response to a single injection of hCG in cryptorchid horses.

This research examined how a single injection of human chorionic gonadotrophin (hCG) impacted the concentration of androgen and estrogen hormones in normal, cryptorchid, and gelding horses. Results indicate the hormone changes may be able to aid in diagnosing cryptorchidism or testicular function in stallions.

Overview of the Research

• The research centered around the effects of a single 10,000 iu injection of human chorionic gonadotrophin (hCG) on the concentration levels of androgen and estrogen hormones in stallions, cryptorchids, and geldings.
• The androgen hormones measured were testosterone and androstenedione, while the estrogen hormones measured were oestradiol -17 beta and oestrone.
• The researchers performed a radio-immunoassay to measure the concentrations of these hormones in the peripheral plasma of the horses.

Findings

• In stallions, the injection led to a quick increase in conjugated estrogens and a more gradual increase in unconjugated androgens.
• In cryptorchid horses, the unconjugated androgens saw a rise following a similar pattern to the stallions, but at lower peak values. On the contrary, the conjugated estrogens experienced only a minor rise.
• The peak levels for estrogen were witnessed two days following the injection, whereas the androgen peak levels were seen a day later.
• For gelding horses, the hCG injection had no effect on the plasma steroid levels.

Implications

• The researchers hypothesize that the analysis of unconjugated androgens before and three days after the hCG injection could help in diagnosing cryptorchidism, a condition where one or both of the testes fail to descend, or could be used to explore testicular function in stallions.