A 15-year-old aquarium-housed female Atlantic walrus (Odobenus rosmarus rosmarus) displayed a bilateral, non-painful, cervical enlargements that have progressed over the last few months. Ultrasonographic examination showed two symmetric, vascularized and oblong masses, non-adherent to deep plans, and located 2.5 to 5 cm from the skin surface. These masses, that were composed of a cystic and vascularized glandular tissue, delineated by a well-demarcated capsule, are highly suggestive of hyperplastic thyroid glands. Over the course of 10 months, the masse’s size increased from 10 cm to greater than 25 cm in diameter, without other clinical signs. Repeated fine needle aspirations of the masses were inconclusive. Hematology and biochemistry showed no significant changes. Total T4 concentrations (9.2 and 9.6 nmol/L) were markedly lower than values documented in wild walruses (unpublished data). Serum TSH levela (7.51 ng/mL) were markedly increased compared to values obtained in three other aquarium-housed walruses (0.06–1.01 ng/ml, n=7 samples). A hypothyroidism was suspected, possibly associated with hyperplastic thyroid glands. The cause of this suspected hyperplastic change remains unclear. Diet modification and medical treatment with levothyroxine was initiated with follow-up TSH level measurements to adjust treatment dose. Even if not reported in the scientific literature, this case, as well as anecdotal reports, suggests that thyroid hyperplastic lesions should be considered in the presence of cervical enlargement in this species. The TSH values obtained with the test used here suggest that this essay is of potential diagnostic interest for the monitoring of thyroid function in walrus.
a IMMULITE®, Diagnostic Products Corporation, Los Angeles, CA, 90045–6900, USA
The authors wish to thank the team of veterinarians and veterinary residents, as well as animal care team and trainers for their help with the management of this animal.