Leptin baseline testing has been added to the available test panels at the New York Animal Health Diagnostic Center Endocrinology Section at Cornell University for horses being tested for Equine Metabolic Syndrome (EMS), formerly known as Insulin Resistance (IR). See the protocol outline at
"Leptin is a hormone produced by adipocytes. Leptin is useful for separating hyperinsulinemia caused by EMS or Cushing’s syndrome from other causes, such as laminitis, stress, or non-fasted samples. This test can be performed on the same sample used for the Insulin baseline or ACTH/Insulin combination test."
According to Eleanor Kellon, VMD "The addition of leptin testing to the proxies greatly improves sensitivity. "
Advantages of the Leptin/Insulin baseline or Leptin/ACTH/Insulin combination tests are they only require a single blood draw (though samples do require special handling and overnight shipping for accurate results).
The Leptin/Insulin baseline or Leptin/ACTH/Insulin combination panels are currently only available through the lab at Cornell, so your veterinarian will need to have an account with Cornell.
For more information, help and support for you and your horse with IR/EMS or PPID (Cushing's) you can join the ECIR Yahoo group at http://pets.groups.yahoo.com/group/EquineCushings/ (the digest or reading web-based posts is recommended as there may be 50 or more messages a day).