Controversies in the Management of Feline Hyperthyroidism — Surgical Excision

Hottinger H.A.

Conference Proceedings, (1998). American College of Veterinary Internal Medicine, San Diego: p.370


The surgical management of feline hyperthyroidism is associated with many benefits compared to prolonged medical management and a few benefits compared to radioiodine therapy. Surgical therapy is not with out its drawbacks and complications,however. Therefore, it is best to weigh the pros and cons of each type of therapy and choose the one that is best suited to an individual


Surgical excision of the thyroid glands allows for a rapid and definitive correction of the condition. The need for daily administration of medication to a patient thai is often difficult to medicate is no longer required. And because the majority of hyperthyroid cats require medication on a BID to TID schedule,the owner’s life style and daily activities are no longer dictated by their eat’s medication schedule. Surgery is also a favorable alternative for those cats that experience side effects from methimazole.

Surgical management of feline hyperthyroidism can also offer benefits over I-131 in certain situations. Surgical excision may be preferred for adenomatous masses of large volume which may not be completely controlled by the standard doses of radioiodine. Adenocarcinomas may be best treated with surgery as well,compared to the high doses of I-131 required to treat them. Some owners may find the length of quarantine required by their state’s radiation board unacceptable, and will choose surgery due to the shorter hospitalization time. Cats in a debilitated state, and especially those with chronic renal disease, may be difficult to manage during the quarantine period if adequate nursing care is not available in that area of the hospital. Surgical management may be elected in this situation as well. And finally, the availability of radioiodine therapy may not be geographically feasible for many pet owners.

The risks of surgery and the potential postoperative complications must also be kept in mind when choosing surgical management of feline hyperthyroidism. In the hands of an experienced surgeon the surgical procedure itself can be very rapid, but even a short anesthetic time can be high risk in many of these patients. If hypertrophic cardiomyopathy is present. it should be controlled prior to surgery, and even then, the patient should be monitored closely for the development of arrhythmias. During surgery, the parathyroid glands must be carefully preserved. The artery supplying the cranial gland is very small and can easily spasm from surgical trauma. Postoperative, the patient should have 24 hour monitoring for at least 48 hours to watch for the development of

hypocalcemia. Should this complication occur, the patient’s hospitalization period is usually prolonged, the financial expenditure increases and medical management and periodic blood tests arc required for 4 to 12weeks. This complication is not a concern with radioiodine therapy. The rate of recurrence is also greater with surgical therapy than with radioiodine. Surgery does not address

ectopic tissue that may be present and could become adenomatous in the future. It is also possible for adenomatous or hyperplastic cells to be left behind when entering the capsule of the gland to dissect and preserve the parathyroid gland.

Although radioiodine therapy has become a mainstay of treatment for feline hyperthyroidism, surgery is still indicated in many instances. If the risks of surgery are kept in mind when this treatment is chosen, a positive outcome can be achieved.