Hyperthyroidism in Domestic Medium Hairs
Hyperthyroidism is the most common endocrine disease in Domestic Medium Hairs over age 7, caused by an overactive thyroid gland (usually a benign tumor) producing excess thyroid hormone. This speeds up metabolism to a dangerous level, causing weight loss, heart damage, and kidney stress. The condition is highly treatable — radioiodine therapy is curative, and daily medication controls it effectively.
Prevalence
Very common — affects 10% of cats over 10 years
Typical Onset
10-15 years
Severity
Moderate
Symptoms to Watch For
If your Domestic Medium Hair shows any of these signs, monitor closely and consult your veterinarian.
Risk Factors
- •age over 7 years
- •indoor lifestyle
- •canned food diet (possible BPA exposure)
- •exposure to flame retardants in household dust
- •non-Siamese breeds (Siamese appear somewhat protected)
Diagnosis
Elevated total T4 is diagnostic in most cases. If T4 is normal but clinical suspicion is high, free T4 by equilibrium dialysis is more sensitive. Thyroid scintigraphy (nuclear scan) localizes the overactive tissue — essential before radioiodine treatment. Blood pressure measurement (hypertension is common). Full blood work to assess kidney function (treatment can unmask renal disease).
Treatment
Radioiodine (I-131) therapy is the gold standard — curative in 95% of cases with a single treatment. Methimazole (oral or transdermal) provides medical management — effective but lifelong. Surgical thyroidectomy is curative but carries anesthetic and parathyroid damage risk. Hill's y/d diet (iodine-restricted) can control mild cases. Always monitor kidney values — treating hyperthyroidism may reveal underlying kidney disease.
Prevention
No proven prevention. May be linked to BPA exposure from canned food linings, flame retardants in household dust, and iodine fluctuations in diet. Annual blood work in cats over 7 years catches it early. Use BPA-free bowls.
When to See a Vet
See your vet if your senior cat is losing weight despite eating well, seems hyperactive, or has a fast heart rate. Blood work provides a quick answer. Untreated hyperthyroidism damages the heart and kidneys.
Other Health Conditions in Domestic Medium Hairs
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