Based on the continuing education webinar presented by Dr. Kristin Marzin, DVM*
Feline hyperthyroidism affects 10% of geriatric cats, making it the most common endocrine disorder in veterinary medicine. Yet for many practitioners, diagnosing borderline cases remains frustratingly difficult. Does this scenario sound familiar? You have a 12-year-old cat with weight loss and a palpable thyroid nodule, but the T4 comes back normal. Do you treat? Wait and retest? Send out for more diagnostics and wait days for results?
Traditional testing methods leave veterinarians in diagnostic gray zones far too often—and waiting for send-out labs delays treatment decisions. The TRUFORMA® platform’s feline-specific TSH test changes that, offering the sensitivity and specificity needed to confidently diagnose hyperthyroidism in 20 minutes, right in your clinic.
The Problem: Total T4 Testing Misses Up to 10% of Hyperthyroid Cats
While approximately 90% of hyperthyroid cats can be diagnosed through clinical signs and elevated T4, a significant percentage of cases fall into diagnostic gray zones. Several factors complicate diagnosis:
- Early disease stages where T4 values haven’t elevated yet
- Normal T4 fluctuations that may drift in and out of reference ranges
- Non-thyroidal illness that can suppress T4 values into normal ranges
The 2016 AAFP guidelines for hyperthyroid management organize these challenging cases into six categories, with most requiring either repeated T4 testing or additional thyroid hormone testing to confirm or exclude hyperthyroidism.
Why Free T4 Falls Short in Real-World Practice
Traditionally, free T4 (measured by equilibrium dialysis) has been used to support hyperthyroid diagnosis in cats, offering nearly 99% sensitivity. However, this highly sensitive test has limitations:
- Free T4 can be normal, increased, or decreased in cats with non-thyroidal illness
- Should not be used as the sole confirmatory test
- Newer chemiluminescent methods show questionable accuracy, consistently undervaluing results compared to equilibrium dialysis
- Not recommended for monitoring cats following radioactive iodine therapy
Feline TSH vs. Canine TSH: Why Species-Specific Testing Matters
In hyperthyroid cats, autonomously secreted thyroid hormones suppress TSH production to near-zero levels—a finding that should make TSH testing ideal for diagnosis. The problem? Canine TSH assays weren’t designed for feline physiology.
- Normal feline TSH range is often lower than the canine assay’s lower limit of quantification
- Canine TSH cannot reliably differentiate between healthy cats and those with non-thyroidal illness
- Cannot be used as a sole diagnostic test
Despite these limitations, research by Dr. Mark Peterson’s group examining 917 hyperthyroid cats demonstrated that serum TSH concentrations are suppressed in 98% of hyperthyroid cats, with median TSH below 0.03 ng/mL compared to 0.05 ng/mL in clinically normal cats. The study found that only 2% of hyperthyroid cats had measurable canine TSH concentrations, while nearly 70% of euthyroid cats had detectable levels. This meant that finding a measurable canine TSH could help rule out hyperthyroidism in cats, though the test showed poor specificity (69.9%) when used alone.
The key insight: while canine TSH could be somewhat useful for screening, its lack of sensitivity in the low range where feline values typically fall—combined with poor specificity—highlighted the critical need for a feline-optimized assay.
How the TRUFORMA® Platform's Feline TSH Test Solves the Diagnostic Puzzle
Zomedica developed the TRUFORMA biosensor testing platform’s feline-verified TSH test to address every limitation of canine assays—with technology optimized specifically for feline physiology and delivered through the only in-clinic platform available. Here’s what makes the TRUFORMA® platform test different:
The Only In-Clinic Feline TSH Test Available
The TRUFORMA system is the only point-of-care platform offering feline-specific TSH testing. Get accurate results in 20 minutes—no send-outs, no waiting, no delayed treatment decisions. Diagnose and create treatment plans in the same appointment, improving both patient outcomes and client satisfaction.
3X More Sensitive Than Canine TSH
The TRUFORMA platform’s feline TSH test has a lower limit of detection of 0.008 ng/mL compared to 0.03 ng/mL for canine TSH—providing the precision needed to accurately measure feline TSH values in the critical low range where feline physiology operates.
Prevents Misdiagnosis in 12% of Healthy Cats
TRUFORMA platform test clinical data from 170 feline samples revealed:
- 95% of healthy cats had serum TSH above 0.01 ng/mL
- 93% of hyperthyroid cats had TSH below 0.01 ng/mL
- 12% of normal cats tested below the canine assay’s detection limit but had measurable TSH with the TRUFORMA platform test—preventing false positive diagnoses and unnecessary treatment
Proven Precision You Can Trust
The TRUFORMA platform’s multi-instrument testing showed coefficient of variation less than 10%—2.5X better than industry standards—ensuring consistent, reliable results.
Critical Application: Detecting Iatrogenic Hypothyroidism
Here’s a sobering statistic: Nearly 50% of treated hyperthyroid cats develop iatrogenic hypothyroidism, regardless of treatment method. Even more concerning? T4 monitoring alone misses almost 80% of these cases.
Why does this matter for your patients?
- Decreased GFR and progression to azotemic chronic kidney disease
- 50% shorter median survival time in cats that become azotemic
- Subtle clinical signs easily missed or attributed to aging
The solution: The TRUFORMA platform’s T4 test and feline TSH test combination identifies these cases early. When you see low or low-normal T4 with elevated TSH, you can adjust methimazole doses or add thyroid supplementation before kidney damage progresses—all with same-day results that enable immediate intervention.
Catching Hyperthyroidism Earlier: The TRUFORMA Platform Advantage
Traditional send-out testing often catches hyperthyroidism only after significant organ damage has occurred—and delays treatment by days while you wait for results. The TRUFORMA biosensor testing platform changes this timeline by identifying cats in the earliest disease stages with same-appointment results, enabling intervention when it’s most effective and before irreversible complications develop.
Early detection means:
- Prevention of cardiac remodeling and hypertension
- Reduced risk of kidney damage from hyperfiltration
- Better treatment outcomes with less aggressive intervention
- Improved quality of life for your feline patients
The Research Behind the TRUFORMA Platform's Feline TSH Test
Recent peer-reviewed research published by Dr. Mark Peterson compared the TRUFORMA platform’s feline-optimized TSH assay with chemiluminescent canine TSH testing across multiple patient populations: hyperthyroid cats, radioiodine-treated cats, chronic kidney disease patients, and healthy cats.
The verdict? The TRUFORMA platform’s feline-specific test demonstrated superior sensitivity and specificity across all groups, offering a more practical alternative to thyroid scintigraphy for practices without nuclear medicine capabilities—with the critical advantage of in-clinic results in 20 minutes.
Implementing The TRUFORMA Biosensor Testing Platform in Your Practice
The TRUFORMA platform’s T4 + feline TSH is becoming the new diagnostic standard, replacing the T4/free T4 send-out combination for hyperthyroid workup. The TRUFORMA in-clinic biosensor testing platform offers value across your entire case management workflow:
✓ Initial diagnosis of suspected hyperthyroidism—results in 20 minutes
✓ Routine wellness screening in geriatric cats during annual exams
✓ Treatment monitoring to prevent iatrogenic hypothyroidism
✓ Differentiating subclinical hyperthyroidism from non-thyroidal illness
Same-day diagnosis means same-day treatment decisions—improving patient outcomes, increasing client satisfaction, and eliminating the frustration of waiting for send-out results while your patient continues to deteriorate.
Ready to bring same-day feline hyperthyroid diagnosis to your practice? The TRUFORMA in-clinic biosensor testing platform is the only point-of-care system offering feline-specific TSH testing. Get accurate results in 20 minutes and make confident treatment decisions in the same appointment.
*Dr. Marzin is a Zomedica Professional Services Veterinarian and was paid for this presentation. Watch the full presentation here.
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