Post‐radiotherapy hypothyroidism in dogs treated for thyroid carcinomas

Abstract

AbstractHypothyroidism is a common adverse event after head and neck radiotherapy in human medicine, but uncommonly reported in canine patients. Records of 21 dogs with histologically or cytologically confirmed thyroid carcinoma receiving definitive or hypofractionated radiotherapy were reviewed. Nine cases received48 Gyin 12 fractions, 10 received36 Gyin 4 fractions and 2 received32 Gyin 4 fractions. Seventeen cases had radiotherapy in a post‐operative setting. Ten cases developed hypothyroidism (47.6%) after radiotherapy. The development of hypothyroidism was not associated with the radiotherapy protocol used. Median time to diagnosis of hypothyroidism was 6 months (range, 1–13 months). Hypothyroidism is a common side effect following radiotherapy for thyroid carcinomas. Monitoring of thyroid function following radiotherapy is recommended. No specific risk factors have been identified.