Evidence of boldenone, nandrolone, 5(10)-estrene-3β-17α-diol and 4-estrene-3,17-dione as minor metabolites of testosterone in equine.

This research has revealed that the compounds boldenone, nandrolone, 5(10)-estrene-3β,17α-diol, and 4-estrene-3,17-dione, previously considered ‘testicular’ steroids, are indeed minor metabolites of testosterone in male castrated horses, also known as geldings. The paper appends that the presence of these metabolites, along with elevated levels of testosterone, in the urine of geldings warrants caution in interpreting results.

Experiments and Findings

• The authors investigated the connection between testosterone and four other steroid compounds in geldings: boldenone, nandrolone, 5(10)-estrene-3β,17α-diol, and 4-estrene-3,17-dione.
• The research was sparked by the detection of these ‘testicular’ steroids in a urine sample from a gelding that had been treated with testosterone.
• Following testosterone treatment in six geldings, researchers were able to confirm that these four steroid compounds could be detected in urine samples post administration.
• This finding suggested to researchers that the four compounds might be minor metabolites of testosterone in geldings, a new identification that has not yet been reported in scientific literature.

In-vitro Experiments

• In vitro experiments conducted by the researchers provided evidence that contradicted their initial findings.
• Experiments involved the incubation of testosterone with horse liver microsomes, liver, adipose and muscle tissues, and adrenal cortex homogenates.
• The researchers failed to find evidence in these tests that the aforementioned four substances were metabolites of testosterone, leading to a contradiction with the initial urine tests results.

Administration Trial

• To resolve the contradiction, the researchers followed up with an administration trial using Testosterone Suspension treated with a C-labeled testosterone, to track testosterone metabolism in the body.
• The similarities between excretion curves of the testosterone variants suggest negligible kinetic isotope effect.
• Of the four supposed metabolites, only boldenone, nandrolone, and 4-estrene-3,17-dione were detected, with the compound 5(10)-estrene-3β,17α-diol notably absent. This provided the obvious evidence that these compounds are indeed metabolites of testosterone in geldings.

Cautious Interpretation

• The study concludes that the presence of the metabolites boldenone, nandrolone and 4-estrene-3,17-dione along with high levels of testosterone in gelding urine could be misconstrued in test results.
• The researchers advocate for careful interpretation of these findings in geldings, promoting alertness to these metabolite variations in geldings.