Equine Endocrinology

Overview of Equine Endocrine Diseases

  • Common endocrine disorders in horses:

    • Equine Metabolic Syndrome (EMS)

    • Pituitary Pars Intermedia Dysfunction (PPID)

  • Importance of recognizing symptoms, signalment, and management strategies.

Key Objectives

  • Compare and Contrast EMS and PPID

    • Signalment

    • Clinical Presentation

  • Design Testing Strategies

  • Develop Management and Therapeutic Strategies

Signalment and Clinical Presentation

Equine Metabolic Syndrome (EMS)

  • Prevalent in:

    • Younger to middle-aged horses (not typically 19 years or older)

    • Breeds particularly affected: Peruvian Pasos, Pony breeds, Morgans

  • Clinical Signs:

    • General obesity

    • Abnormal fat deposition (especially neck crest, tail head, and sheath in geldings)

    • Increased risk of laminitis

    • Difficulties in breeding for mares

Pituitary Pars Intermedia Dysfunction (PPID)

  • Commonly seen in:

    • Older horses (usually >15 years old; often diagnosed around 19-21 years)

    • Some breeds like ponies may be predisposed, but this is less common now

  • Clinical Signs:

    • Hypertrichosis (longer hair coat; not hirsutism)

    • Muscle wasting leading to potbellied appearance

    • Increased risk of laminitis

    • Infections (secondary due to hormonal imbalance)

Differentiating Between EMS and PPID

  • Clinical Signs: look for overlaps

  • Signalment: age, body condition, and breed can provide important context

  • Emphasize testing if clinical signs are vague; don’t rule out EMS based solely on age or presentation

Testing Strategies for EMS

  • Resting insulin and glucose tests:

    • High insulin levels indicative of insulin resistance

    • Look for insulin dysregulation, but this alone does not confirm EMS

  • Dynamic Tests:

    • Oral Sugar Test (Karo syrup): measures insulin response to an oral glucose load

    • Insulin Tolerance Test: assesses glucose response to insulin administration

Testing Strategies for PPID

  • Resting Plasma ACTH Levels:

    • ACTH elevation indicates PPID

  • TRH Stimulation Test:

    • Effective for early detection of PPID; can affirm diagnosis if positive.

  • Dexamethasone Suppression Test:

    • Less commonly used now; not preferred due to variable results

Management and Therapeutic Strategies

EMS Management

  • Focus on:

    • Weight management through diet (low-sugar feeds)

    • Reducing caloric intake

    • Regular exercise

  • Monitor for laminitis

PPID Management

  • Treatment may require lifelong administration of Pergolide.

  • Monitor and reassess every 3-6 months after initiating treatment.

  • Be cautious before starting treatment without definitive diagnosis; consider potential side effects.

Conclusion

  • Regular updates from the Equine Endocrine Group are valuable for current practices.

  • A good understanding of EMS and PPID, along with appropriate diagnostic tests and management strategies, is crucial for effective equine practice.