Hyperthyroidism
Hyperthyroidism is the most common hormone imbalance in cats. It is caused by a benign overgrowth (adenomatous hyperplasia) of thyroid tissue that produces excess thyroxine-t4, driving up the body's metabolic rate. The condition emerged as a recognized disease in the 1980s and predominantly affects senior cats (average age at diagnosis: ~13 years).
Key Facts
- 96-98% of cases are caused by benign thyroid tumors (not cancer)
- Hallmark sign: weight-loss despite an excellent appetite
- Risk factors include age, genetics, indoor lifestyle, and exposure to canned food (BPA in can lining) and environmental chemicals
- Siamese and Himalayan breeds have a decreased incidence
- Untreated hyperthyroidism leads to hypertension and heart-disease
- Species: cats only (dogs are not affected by hyperthyroidism)
Connections (24)
Related Conditions
Treating hyperthyroidism can unmask hidden CKD because hyperthyroidism artificially increases kidney blood flow. Both are common in senior cats.
Both are endocrine disorders of older cats; thyroid disease alters glucose metabolism
Alters glucose metabolism; resolving thyroid disease improves diabetic regulation
Untreated thyroid excess causes cardiac changes that can progress to heart failure and sudden death.
— medical cause of house soiling
Treating the thyroid often resolves the hypertension entirely.
Post-thyroidectomy parathyroid damage causes hypocalcemia
— thyroid disease must be ruled out
In cats, malignant thyroid tumors cause hyperthyroidism
Symptoms
Untreated thyroid disease leads to hypertension, which can cause sudden blindness.
Chronic intermittent diarrhea is a common sign.
Excessive thirst, also an early sign of CKD.
Chronic intermittent vomiting, also seen in CKD and intestinal lymphoma.
The hallmark sign, shared with CKD and lymphoma.
Treatments
Medications
Diagnostics
Body Systems
Source Articles (9)
Backlinks (9)
Endocrine
- Signs, Symptoms, and Diagnosis of Hyperthyroidism in Cats
- Hyperthyroidism Medication for Cats (Methimazole)
- Hyperthyroidism Treatment Options in Cats
- Dietary Therapy for Hyperthyroidism in Cats
- Surgical Treatment for Feline Hyperthyroidism
- Thyroid Treatment Using Radiotherapy for Cats
- Malignant Thyroid Tumors in Dogs and Cats