Presenting complaints commonly include weight loss, PU/PD, vomiting, and hyperactivity.

Up to 26% of all cats with hyperthyroidism have an apathetic presentation.

Hyperthyroidism causes increased appetite so it can be ruled out in anorexic cats.

Hyperthyroidism is the most common endocrine disease affecting cats greater than 8 years of age.

Elevated alanine transferase and/or alkaline phosphatase

Proteinuria

Anemia

Administration of glucocorticoids  

Nonthyroidal illness

Early or mild disease

All of the above can cause a hyperthyroid cat’s tT4 level to be in the reference range.

fT4 is more sensitive and less specific than tT4 in diagnosing feline hyperthyroidism.

TSH is typically elevated in hyperthyroid cats.

If only one test is to be run, fT4 testing is preferred over tT4.

Hyperthyroidism should never be diagnosed based on tT4 alone.

Proteinuria typically warrants specific antiproteinuric therapy even after hyperthyroidism is treated.

All cats should be treated with a reversible therapy (eg, methimazole) before an irreversible one (eg, radioactive iodine) to ensure they do not develop azotemia.

Renal function can only be fully assessed using serum creatinine concentrations after euthyroidism is established.

Cats whose tT4 concentrations drop below the normal reference range never require dose adjustment of antithyroid medication if they are not azotemic.

should be managed according to IRIS guidelines for the management of feline CKD.

have worse survival times than cats that remain nonazotemic.

should have a target tT4 concentration in the upper half of the laboratory reference range.

are not candidates for definitive therapy such as thyroidectomy or radioiodine treatment.

Hepatotoxicity

Blood dyscrasias (eg, neutropenia, thrombocytopenia)

Facial pruritis

GI signs (eg, vomiting, diarrhea, anorexia)

Agitation

Hyperthermia

Respiratory distress

Premedication with atropine or glycopyrrolate

Administration of a β-blocker

Use of an anesthetic chamber for induction

Placement of monitoring equipment after anesthetic induction

positive inotropic, negative chronotropic

negative inotropic, positive chronotropic

positive inotropic, positive chronotropic

negative inotropic, negative chronotropic