Cardiac Disease Related to Primary Hyperthyroidism in a 20-Year-Old Mule

Area of Science:

• Veterinary Medicine
• Endocrinology
• Cardiology

Background:

• Primary hyperthyroidism is rare in equids.
• Cardiac changes associated with hyperthyroidism in equids have not been previously reported.

Observation:

• A 20-year-old mule presented with a three-month history of poor body condition, polyphagia, tachycardia, a heart murmur, and palpable cervical masses.
• Bloodwork revealed elevated thyroid hormone concentrations (free T4, total T4, T3).
• Echocardiography showed left ventricular concentric hypertrophy and increased systolic function.

Findings:

• Thyroid gland histopathology confirmed adenocarcinoma and adenomas.
• Following bilateral thyroidectomy and levothyroxine supplementation, the mule's polyphagia resolved and weight improved.
• Echocardiographic changes showed improvement but did not fully resolve two years post-surgery.

Implications:

• This case represents the first documentation of hemodynamically relevant cardiac remodeling in an equid associated with primary hyperthyroidism.
• It underscores the importance of considering hyperthyroidism in equids presenting with cardiac abnormalities and metabolic signs.
• Further research into equine hyperthyroidism and its cardiovascular effects is warranted.