IF feline hyperthyroidism is not on your radar then perhaps you need to tweak your settings. Following Dr Sarah Caney’s assessment of treatment modalities at the BSAVA congress, questions should be asked about how we effectively monitor a condition that affects approximately 12% of cats over the age of nine in the UK.
Of eight million cats, around half are in that age range, meaning hyperthyroidism affects more than 300,000 cats. “It is a huge number,” Sarah says, but the fact is that the lack of a treatment gold standard, range of severity and complications with concurrent illness – such as kidney disease – make this a complex clinical problem.
“More and more we need to look at the individual cat and its circumstances then suggest a plan that is most appropriate,” she says. “From a prognosis perspective, radio-iodine is the least routinely performed because of its availability but it has the best results for long-term survival.
“If it is completely healthy and quite young you might encourage the owner to consider surgery. If the cat has heart or kidney disease, then it might not be a good option. There is now a nutritional option that allows you to manage the condition using food, but there is no absolute gold standard.”
Sarah, whose Cat Professional practice provides specialist advice, revealed details of an online survey among cat owners into their attitudes to antithyroid medication. Of 111 respondents, the majority view was that medication, given once or twice daily, is readily acceptable.
“We were biased towards owners who used oral medication,” she says. “If you did that survey with 100 cat owners in the street, they might fret about giving their cat a pill every day. But if we ask what client concerns are, their experiences and where they feel they need education and support, hopefully we do a better job to provide it and get better treatment outcomes.”
Sarah has also estimated how many cases are diagnosed. “That is another hurdle,” she admits. “It is not as cut and dried to diagnose, though we are more attuned to making the diagnosis than we were. It raises some problems in that patients we see are earlier in the disease and their lab results are not quite as convincing, making it harder to nail down.
“In practices I’ve worked there are still plenty of cases that are undiagnosed or under-diagnosed, either because owners do not recognise clinical signs or realise their significance, or because vets do not.”
Despite the uptake of thyroid testing in the health screening of older cats, leading in some cases to false positives, concurrent illnesses like diabetes serve to muddy the waters further. “People say ‘well it has diabetes so I don’t need to look for other conditions’,” says Sarah.
Typically, hyperthyroidism means increased appetite and heart rate are supplemented by other factors such as unkempt coat, diarrhoea, plus increased urination and drinking. An enlarged thyroid in the neck is the tell-tale sign. Kidney problems are another.
Despite the efficacy of radio-iodine and surgical intervention, there is a need to manage cases carefully. Imbalances can occur and vets should be aware that hypothyroidism can follow treatment, with real impacts on renal function and longevity.
“It is early days but some studies have suggested that up to half of cats treated with radioiodine develop hypothyroidism,” Sarah says. “You would certainly want to treat medically for at least a month – several from my own experience – before going on to curative options.
“Manage by starting off with something that is a revertable treatment – use something that can be titrated or controlled. I’m a big fan of starting with a low dose of anti-thyroid medication. From my own experience it is better tolerated by cats and less likely to induce side effects like nausea or appetite suppression. In the case of diet, that can be withdrawn if need be.”
Sarah’s study subjects were owners who ranked dose accuracy as most important (85%) along with lower medical doses. Most (80%) said twice daily medication was not a problem, with only 12% in disagreement.
“They probably are owners who struggle on a daily basis with treatment,” admits Sarah.
“This is one of the most important outcomes because certainly when I talk about hyperthyroidism to vets, quite often they say that once-a-day treatment is what they aim for because you get best compliance from owners and a better outcome. For these owners that was not the case.”
Sarah’s contention is that we should not make assumptions about how owners feel. Neither should survey results be accepted blithely. “The sensible thing is to fully inform and involve owners in decisionmaking. If first choice treatment is not appropriate, then at least you have had the discussion.”
Utilising nurses to provide education and support is the effective way to help concerned clients. “A lot of respondents said they would like support on how to give a pill,” says Sarah. “We are good at prescribing medicines but not necessarily at providing assistance or guidance on giving a pill to their cat. That is the perfect thing for a nurse to do.”
Ultimately, until we fully understand what causes hyperthyroidism there will be no magic bullet. “At this stage it is more about increasing understanding,” she concludes. “That means making a diagnosis in a tricky case, or being aware of over-diagnosing when you are screening elderly healthy cats and questioning lab results if they do not fit the patient.”