I have a 12 year old male neutered Maine coon cat that has a free T4 (measured by equilibrium dialysis) of 57.9 nmol/L (normal is up to 50 nmol/L). The cat has stable weight and no real signs of hyperthyroidism. Other blood is good. Just wondering how we should follow up. I am contemplating re-assessing in a month or two? What is the correct approach to this case?
Thanks in advance.

My Response:

Monitor the cat's body weight, heart rate, thyroid size, and serum total T4 concentrations every 2-3 months.

Hyperthyroidism is a clinical diagnosis. The finding of a high serum free T4 value means nothing unless you have clinical signs, or a palpable thyroid nodule, or both.

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