Animal Endocrine Clinic: Is a High Serum T4 or Free T4 Level Always Diagnostic for Hyperthyroidism in Cats?

Thyroid scan (scintigraphy) in a cat suspected of hyperthyroidism. Both thyroid lobes are of normal size and shape. Uptake of the radionuclide by the thyroid is also normal, with a thyroid/salivary ratio of 0.8 (normal <1.5). This is a normal study and rules out hyperthyroidism. 
Scintiscan provided by Dr. Michael Broome, Advanced Veterinary Medical Imaging 

Just posted this on my other blog for pet owners but it's relevant information for veterinarians and veterinary technicians as well. To read more, click below:

Animal Endocrine Clinic: Is a High Serum T4 or Free T4 Level Always Diagnostic for Hyperthyroidism in Cats?