True hypothyroidism is rare in adult horses and is commonly misdiagnosed (MSD). The clinically important form is congenital hypothyroidism in foals. The exam point is the opposite of what many students expect: an obese, cresty-necked, laminitic horse with a low thyroid hormone result does not have hypothyroidism. It has insulin dysregulation (equine metabolic syndrome, EMS) or pituitary pars intermedia dysfunction (PPID).
Key facts
Hypothyroidism at a glance- Species and system: horse; endocrine.
- Adults: hypothyroidism appears rare and is commonly misdiagnosed (MSD).
- Foals: congenital hypothyroidism may follow mares grazing goitrogenic plants or having too little or too much iodine; thyroid hyperplasia with musculoskeletal deformities has been linked to high-nitrate diets (MSD).
- Test pitfall: low total T4 occurs with many non-thyroidal causes; a low value alone is not diagnostic.
- Treatment: levothyroxine labeled for horses with hypothyroidism.
- Zoonotic: no.
What's inside
12 sections in the full guide- Key facts
- How the NAVLE tests this
- Cause and pathophysiology
- Clinical signs
- Diagnosis
- Differential diagnoses
- Treatment and management
- Putting it together in practice
- Prognosis
- Quick review
- Test yourself
- References
The full guide also has 5 tables, 3 self-test questions and 6 references, available to NAVLE members.
Read the full study guide
The full guide is part of every NAVLE plan, with diagnosis and treatment tables, figures, a quick review and self-test questions. Start a free trial to try the question bank, or log in if you are already a member.