Tentative Diagnosis: The tentative diagnosis is Feline Hyperthyroidism. The classic signalment (older cat), hallmark history (weight loss despite polyphagia, PU/PD, hyperactivity), and cardinal physical exam findings (thin body condition, tachycardia, heart murmur, and a palpable thyroid slip) create an almost textbook presentation for this disease.
DDx: For an older cat presenting with weight loss and PU/PD, the primary differential diagnoses include Chronic Kidney Disease (CKD) and Diabetes Mellitus. Gastrointestinal disease, such as inflammatory bowel disease or lymphoma, could also cause weight loss but would not typically explain the hyperactivity and polyphagia.
Further Diagnostic Test(s): While the clinical suspicion is extremely high, a definitive diagnosis requires hormone testing.
Definitive Screening Test: The single most important test is a serum Total T4 (TT4) concentration.
Result: Jasper's serum TT4 was 9.5 µg/dL (Markedly High) [Ref: 0.8 - 4.0 µg/dL].
Interpretation: A TT4 level this far above the reference range in a cat with classic clinical signs is definitively diagnostic for hyperthyroidism.
No further thyroid-specific testing is needed. The elevated blood pressure reading confirms concurrent systemic hypertension, a common and serious complication.
Definitive Diagnosis:
Feline Hyperthyroidism with secondary systemic hypertension. For more, see the
Treatment Plan: The treatment plan involves stabilizing the patient, managing comorbidities like hypertension, and then discussing options for a permanent cure with the owner.
Initial Medical Stabilization:
Antithyroid Medication: Jasper was started on Methimazole (2.5 mg orally twice daily). This medication blocks the synthesis of new thyroid hormones and will manage the clinical signs.
Antihypertensive Medication: To manage the high blood pressure and protect his eyes, kidneys, and heart, Jasper was also started on Amlodipine (0.625 mg orally once daily).
Monitoring and Staging:
A recheck appointment was scheduled for 2 weeks. At this visit, his blood pressure, T4 level, and kidney values (BUN, creatinine) will be re-evaluated. It is critical to monitor kidney function, as the high blood pressure and increased metabolic rate of hyperthyroidism can increase blood flow to the kidneys, potentially "masking" underlying chronic kidney disease. Treating the hyperthyroidism may cause a decrease in this blood flow, revealing the underlying condition.
Discussion of Long-Term Options:
The owner was counseled that while methimazole is effective, it is not a cure and requires lifelong medication.
The gold standard treatment, Radioactive Iodine (I-131) therapy, was strongly recommended. This is a single subcutaneous injection that is curative in over 95% of cases.
Other definitive options, such as surgical thyroidectomy and a prescription iodine-limiting diet (Hill's y/d), were also discussed as alternatives.
No comments:
Post a Comment