Medical management of hyperthyroidism.
Radioiodine is considered the treatment of choice for hyperthyroidism, but in some situations, methimazole therapy is preferred, such as in cats with pre-existing renal insufficiency. Methimazole blocks thyroid hormone synthesis, and controls hyperthyroidism in more than 90% of cats that tolerate the drug. Unfavorable outcomes are usually due to side effects such as gastrointestinal (GI) upset, facial excoriation, thrombocytopenia, neutropenia, or liver enzyme elevations; warfarin-like coagulopathy or myasthenia gravis have been reported but are rare. Because restoration of euthyroidism can lead to a drop in glomerular filtration rate, all cats treated with methimazole should be monitored with BUN and creatinine, in addition to serum T4, complete blood count, and liver enzymes. Transdermal methimazole is associated with fewer GI side effects, and can be used in cats with simple vomiting or inappetance from oral methimazole. Hypertension may not resolve immediately when serum T4 is normalized, and moderate to severe hypertension should be treated concurrently with-atenolol, amlodipine, or an ACE inhibitor. Alternatives to methimazole include carbimazole, propylthiouracil, or iodinated contrast agents.
Department of Medical Sciences, University of Wisconsin-Madison, Madison, WI, USA. latrepanier@svm.vetmed.wisc.edu
Lauren A
LA
Trepanier
D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D000818:Animals; D013956:Antithyroid Agents / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D002231:Carbimazole / Q000627:therapeutic use; D002371:Cat Diseases / Q000188:drug therapy*; D002415:Cats; D003287:Contrast Media / Q000627:therapeutic use; D006980:Hyperthyroidism / Q000188:drug therapy / Q000662:veterinary*; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D007462:Iodobenzenes / Q000627:therapeutic use; D008713:Methimazole / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D011441:Propylthiouracil / Q000627:therapeutic use; D016896:Treatment Outcome
D000319:Adrenergic beta-Antagonists; D013956:Antithyroid Agents; D003287:Contrast Media; D007457:Iodine Radioisotopes; D007462:Iodobenzenes; D008713:Methimazole; D011441:Propylthiouracil; D002231:Carbimazole