Hyperthyroidism or excess thyroid hormone production is a common problem in older cats. For unknown reasons,some cats develop tumors on their thyroid glands as they age. Although the majority of these tumors are considered benign because they do not metastasize, that does not mean that they do not affect the cat. Thyroid ademonas secrete large quantities of thyroid hormone, far more than what the cat needs. The high level causes a host of effects all related to an increased metabolic rate.
Clinical signs of hyperthyroidism:
1) Tachycardia (increased heart rate usually over 200 bpm).
2) Gallop rhythm.
3) Weight loss even though the cat eats well.
4) Increased activity. People often tell me the cat is running around like a kitten.
8) A thyroid nodule felt on the cat’s neck.
9) Acute blindness caused by retinal detachment secondary to the hypertension.
10) Vocalization. Cats meow in a long, drawn out fashion.
*In my experience, weight loss is the most common sign of hyperthyroidism.