Is Your Cat Losing Weight But Still Eating? It Might Be Hyperthyroidism
You might think a cat who’s eating like a lion but still losing weight is just being quirky—but it could be a sign of something more serious: hyperthyroidism. At PetMed of Key West Veterinary Clinic in Dubuque, hyperthyroidism is one of the most common hormonal conditions we diagnose in senior cats—and thankfully, it’s also one we can manage very effectively.
Fun Fact: Dogs and Cats Are Thyroid Opposites!
Here’s a quirky little truth from the exam room:
- Dogs are almost always hypothyroid (their thyroid slows down)
- Cats are almost always hyperthyroid (their thyroid speeds up)
So while dogs tend to get sluggish and gain weight, hyperthyroid cats are typically bouncing off the walls and losing pounds—even while eating nonstop.
Signs of Hyperthyroidism in Cats
Hyperthyroidism occurs when the thyroid gland produces too much thyroid hormone, revving up your cat’s metabolism and overworking nearly every system in the body.
Common signs include:
- Weight loss despite a normal or increased appetite
- Increased thirst and urination
- Hyperactivity or restlessness
- Vomiting or diarrhea
- Unkempt or greasy coat
- Rapid heart rate
- Muscle wasting, especially along the spine
- Panting or difficulty breathing in severe cases
These changes often come on gradually and may be mistaken for “just getting old,” but left untreated, hyperthyroidism can lead to heart disease, high blood pressure, and kidney damage.
How We Diagnose It
Diagnosis is typically straightforward: a simple blood test to check T4 (thyroxine) levels. In some cases, we may run additional tests like Free T4 or thyroid panels to confirm the diagnosis or assess disease severity. We also recommend checking kidney values, blood pressure, and heart health, since these can be affected by or influence treatment decisions.
Treatment Options for Feline Hyperthyroidism
One of the great things about this disease is that we have multiple ways to treat it, depending on what works best for your cat—and your household.
Methimazole (Anti-Thyroid Medication)
This is the most common starting point. Methimazole blocks the thyroid from overproducing hormones and comes in several forms:
- Tablet given once or twice daily
- Oral liquid is great for picky cats
- Topical gel which is applied to the inner ear skin
We monitor T4 levels and adjust the dose as needed. Most cats tolerate it well with few side effects, though it’s not a cure—it’s a lifelong treatment.
Prescription Diet: Hill’s y/d
Hill’s y/d is a specially formulated iodine-restricted diet that can significantly reduce thyroid hormone production—if and only if it’s fed strictly. That means no treats, no other food, and no table scraps. For cats in single-pet households who are food-motivated, this can be a great non-medication option. It’s not for every cat, but it’s worth discussing!
Radioactive Iodine Therapy (I-131)
This treatment is considered the closest thing to a cure. A single injection of radioactive iodine destroys the overactive thyroid tissue—without harming the rest of the body.
The catch? I-131 requires specialized facilities, a short hospital stay, and a period of isolation after discharge. The nearest treatment centers to Dubuque are typically located near the Chicago area. We’re happy to help with referrals if you’re interested in this option.
Long-Term Monitoring
Regardless of the treatment path you choose, your cat will need routine labwork to monitor thyroid hormone levels, kidney function, and overall health. Some cats with underlying kidney disease may need a gentler approach or closer follow-up, which we tailor on a case-by-case basis.
Don’t Ignore the Signs. Call PetMed of Key West Today
If your senior cat is losing weight, acting strangely, or eating more than usual without gaining, it’s time to check their thyroid. The sooner we diagnose hyperthyroidism, the better the outcome. Call PetMed of Key West Veterinary Clinic in Dubuque today to schedule a wellness exam or thyroid screening. Let’s keep your cat purring, playful, and on the right track—at the right speed!