Thyroidectomy

For cats with hyperthyroidism, thyroidectomy is one of three curative options alongside radioactive iodine (I-131) and a prescription iodine-restricted diet. Surgery tends to be recommended when:

• The cat has unilateral disease (one gland affected) with good surgical risk — cure rates approach 95%
• Radioactive iodine is not accessible or the owner prefers a local procedure with rapid resolution
• Concurrent conditions make long-term medication management difficult

For dogs with thyroid carcinoma, surgery is the primary treatment when imaging confirms the mass is resectable — chemotherapy or radiation may complement surgery depending on tumor staging and completeness of excision.

Thyroidectomy is performed under general anesthesia with full cardiovascular monitoring — cats with hyperthyroidism are at elevated cardiac risk and require careful anesthetic management. The surgical steps:

• A ventral (underside of neck) incision is made over the thyroid region
• The affected gland(s) are carefully dissected free from surrounding structures, including the major carotid vessels and the recurrent laryngeal nerves, which control the voice box
• The parathyroid glands — tiny structures on or embedded within the thyroid that regulate blood calcium — are identified and preserved whenever possible
• In bilateral (both-side) cases, the surgeon may stage the procedure or use an intracapsular technique to protect at least one parathyroid gland
• The incision is closed in layers; the procedure typically takes one to two hours

Cats with hyperthyroidism are stabilized on methimazole (thyroid-suppressing medication) for two to four weeks before surgery to normalize thyroid hormone levels and reduce cardiac risk. An echocardiogram (heart ultrasound) is often performed to assess heart function. Pre-anesthetic bloodwork, blood pressure measurement, and neck ultrasound or CT are used to confirm the number of affected glands and plan the surgical approach. Dogs with suspected thyroid carcinoma undergo CT imaging and chest X-rays for staging before proceeding. Withhold food the evening before surgery.

Most cats are discharged one to two days after surgery. Key aftercare considerations:

• Blood calcium is monitored closely in the first 24 to 72 hours post-operatively — low calcium (hypocalcemia) is the most important short-term complication when parathyroid tissue is disrupted
• Signs of hypocalcemia — facial twitching, muscle tremors, or weakness — should prompt an immediate call to the hospital
• Thyroid hormone levels (T4) are rechecked at two to four weeks; some cats require short-term supplementation if levels drop below normal after bilateral surgery
• An Elizabethan collar is worn for ten to fourteen days to protect the neck incision
• Activity is restricted to calm indoor movement during the recovery period

Thyroidectomy carries risks beyond those of general surgery. The most clinically significant are:

• Hypoparathyroidism (low calcium): damage or inadvertent removal of parathyroid tissue causes hypocalcemia, which may require temporary or, rarely, permanent calcium and vitamin D supplementation
• Recurrent laryngeal nerve injury: uncommonly, the nerve controlling the voice box is stretched or damaged, causing voice change or, in severe cases, breathing difficulty
• Hypothyroidism (low thyroid): after bilateral thyroidectomy some cats require thyroid supplementation — a straightforward and inexpensive medication
• Regrowth: ectopic (extra) thyroid tissue in the chest may become active after surgery, causing recurrence of hyperthyroidism months to years later

In experienced hands, serious complications are uncommon, and the large majority of cats with hyperthyroidism are cured by surgery and thrive long-term.