Just because a particular type of anomaly in a horse is rare doesn’t mean it’s not important to investigate and understand better: Take granulosa cell tumors (GCTs), for instance. While these only represent about 2.5% of all equine tumors and usually are benign, GCTs are most common neoplasm (tumor) found in the equine reproductive tract; further, GCTs are difficult to diagnose and can cause a host of problems in affected mares including pregnancy prevention and behavioral problems (i.e., stallion-like behavior).

Veterinarians often detect a GCT during a routine palpation or rectal ultrasound, and currently veterinarians rely on endocrine tests–measuring blood levels of certain hormones such as inhibin, testosterone, and progesterone–to confirm suspicions of a GCT.

However, Barry A. Ball, DVM, PhD, Dipl. ACT, Albert G. Clay Endowed Chair in Equine Reproduction at the University of Kentucky’s Maxwell H. Gluck Equine Research Center, described an alternate blood test that involves measuring the anti-Müllerian hormone (AMH) in his presentation at the 2011 American Association of Equine Practitioners convention, held Nov. 18-22 in San Antonio, Texas.

“My colleagues and I recently discovered that high levels of AMH are produced by GCTs, which circulate in the bloodstream,” relayed Ball