Why Have Cats Started to Suffer from Hyperthyroidism?


Cats / Tuesday, May 23rd, 2017

Hyperthyroidism is a condition which has long been recognised in humans. However, cats were not diagnosed with the condition until the 1970s. Causing weight loss despite a voracious appetite, hyperthyroidism is now instantly recognisable as it has become so common in felines. Which makes you wonder what could have caused such an epidemic?


Could it be that an aspect of our modern lifestyles has led to the prevalence of yet another health issue? One vet in America certainly suspected that this would prove to be the case when he first discovered that so many cats were experiencing thyroid related issues.

The First Case of Hyperthyroidism in Felines

In 1978, New York vet Dr Mark Peterson met Sasha, a cat suffering from severe weight loss with no apparent cause. His colleagues were scratching their heads in despair. Despite never having seen a cat with hyperthyroidism, Peterson wondered if this condition could be to blame and asked a doctor to scan the animal. The scan revealed a benign tumour on the cat’s thyroid gland. One of his colleagues then informed Peterson of five further cats suffering from the same symptoms. These animals were all later found to have compromised thyroid glands.

Hyperthyroidism Across the World

It wasn’t long before Dr Peterson had encountered over 100 cases of the condition. A condition which, until that time, cats had not suffered from. In 1979 Peterson delivered a presentation at a veterinary conference in Seattle in which he outlined five cases of hyperthyroidism in cats. This caused quite a stir and stories of hyperthyroidism in cats across the USA began to emerge. As the years went by more and more cats seemed to be suffering from the condition which was now appearing around the world.

Potential Causes

Treatments for hyperthyroidism were soon developed but it has taken a lot longer to find out why hyperthyroidism seemingly appeared from nowhere. A number of experts, including Dr Peterson, have spent many years researching possible causes all the time suspecting that dietary, environmental or lifestyle factors had to be to blame. Their efforts uncovered a long list of potential suspects but now a front runner has emerged.

Hazardous Chemicals

Polybrominated diphenyl ethers are chemicals which were used as fire retardants in many household items including carpets, underlays, sofas and electrical goods. These chemicals leached into household dust and then settled around homes. The chemicals also happened to possess chemical structures similar to thyroid hormones. These fire retardants were introduced in the 1970s! They have now been withdrawn but take years to degrade and so many households will still be polluted with them.

Born in the USA

The chemicals were first used and most heavily used in the USA which would explain why hyperthyroidism in cats appeared there first. Cats roll on the floor, sit on the sofa and lick themselves and so are likely to ingest any chemical residue which has settled. Researchers had also noted that indoor cats were the most to susceptible to hyperthyroidism and so the fire retardant theory also explains this anomaly.

Hopefully the incidence of hyperthyroidism will now begin to decline. Probably to be replaced by another nasty disease that human lifestyles have caused!

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