02/16/2025
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Many horses on pergolide can still have bouts of foot soreness. Why is this?
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Cushing's alone has proven not to cause laminitis, even microscopically. No laminitis on slides; it needs to be insulin resistance (IR) or IR + Cushing's. Cushing's churns higher IR because Cushing's reduces muscle (biggest user of insulin, so less muscle, higher blood insulin) and because pergolide lowers thyroid levels, which many owners are unaware of. Thyroid powder is proven to cause two times more insulin sensitivity. It is proven as a vasodilator, so more blood flows to the feet. When thyroid levels drop to low or normal levels while on pergolide, feet can get sore.
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Age: Dropping thyroid levels is normal with aging for people and horses. They are lower than usual when pergolide is added, and now they are even lower.
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Olditis: If a horse is on bute or Banamine due to stiffness, that also lowers thyroid levels. Now you have pergolide, age, and certain NSAIDs lowering T4 thyroid levels on blood tests.
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Every horse on pergolide should be tested for T4 thyroid and insulin levels. Most horses will need thyroid powder when on pergolide to maintain high normal levels of T4 (be at A+ normal levels, not Cβbarely okay levels). As they lose muscle from age and Cushing's, IR will increase, so eventually, it will be Cushing's + IR.
Take-home lessons:
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Cushing's alone does not lead to laminitis.
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Pergolide drops thyroid levels.
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As you lose muscle, IR will increase.
Articles on these subjects are available on our website for download, reading, texting, or emailing to others. https://equinemedsurg.com/
Contact Dr. Reilly for more information: https://equinemedsurg.com/pages/contact