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Juvenile-onset hypothyroidism in a dog.
Journal of the American Veterinary Medical Association
|November 1, 1985
Summary
Juvenile-onset hypothyroidism in a dog caused quadraparesis and unusual dwarfism. Primary hypothyroidism may impair growth hormone secretion, mimicking pituitary dwarfism.
Area of Science:
- Veterinary Medicine
- Endocrinology
- Canine Health
Background:
- Juvenile-onset hypothyroidism is a rare endocrine disorder in dogs.
- Congenital hypothyroidism can lead to significant developmental abnormalities.
Observation:
- An adult mixed-breed dog presented with quadraparesis and clinical signs including disproportionate dwarfism, enlarged tongue, mental dullness, and retention of a puppy coat.
- Radiographic findings revealed delayed epiphyseal closure and dysgenesis, with myelography showing intervertebral disk protrusions.
Findings:
- Diagnosis of hypothyroidism was confirmed by low serum thyroxine unresponsive to thyroid stimulating hormone.
- Laboratory findings included anemia, mild hypercalcemia, and impaired growth hormone (GH) secretion after xylazine administration.
- Necropsy revealed a small thyroid gland with glandular tissue loss and replacement by adipose tissue; the pituitary gland was histologically normal.
Implications:
- Primary hypothyroidism can lead to impaired growth hormone secretion, potentially mimicking pituitary dwarfism.
- Differentiating hypothyroid dwarfism from GH deficiency solely on provocative GH testing can be challenging.
- This case highlights the complex interplay between thyroid hormones and growth hormone regulation in canine development.