WHAT IS THYROID HORMONE?

Active thyroid hormone (nicknamed “T3,” short for “triiodothyronine”) sets the body’s metabolic rate, sort of like a volume dial. One might say T3 determines how hard or how fast each cell works to do its job. Every cell of the body is affected by T3.

The thyroid glands (there’s one gland on each side of the windpipe) do not produce T3. Instead, they produce an inactive form called “T4.” Tissues of the body absorb T4 and convert it to T3.

Doctors will readily make references to T3 and T4. It is a good idea to know what they are referring to. While T3 is the active hormone, it turns out that more meaningful information is gained by measuring T4. Your veterinarian will probably mention monitoring your cat’s T4 level.