Could a simple test of horse hair be developed to diagnose cases of Cushing’s disease in horses?
Austrian researchers studying hyperadrenocorticism in dogs – the equivalent of Cushing’s in horses – have found that analysis of dog hair can provide a quick and reliable diagnosis.
Researchers from the University of Veterinary Medicine, in Vienna, said a surprisingly large number of dogs suffered from the condition.
The symptoms are caused by excessive amounts of hormones – glucocorticoids – in the body.
Unfortunately, diagnosis is complicated by the fact that glucocorticoid levels naturally fluctuate and most methods for measuring the concentration of the hormones in the blood provide only a snapshot of the current situation.
Recent research at the university has shown that glucocorticoids accumulate in the animals’ hair and that analysis of a dog’s hair can provide quick and reliable preliminary diagnosis.
The results are published in the current issue of the journal, Veterinary Dermatology.
Just over a century ago, Harvey Cushing published an account of a young woman who showed unusual symptoms because her glands were making excessive amounts of a substance.
Subsequent research revealed that the agent in question is a set of hormones known as glucocorticoids that are produced by the adrenal glands.
Cushing’s disease is now more commonly known as hyperadrenocorticism, or pars pituitary intermedia dysfunction in horses.
The condition is particularly common in dogs, particularly as the animals grow older. Most cases result from a tumour in the pituitary gland but some relate to tumours in one of the adrenal glands themselves.
One of the main problems with diagnosis is that the symptoms appear only gradually, so owners and vets are initially likely to overlook them or to attribute them to other causes, such as general old age.
Unfortunately, the methods commonly used to test for the condition are complicated and costly – and generally only give information about the hormone concentrations at the time a sample is taken, when the animal might have unusually high levels because of the stress associated with the examination.
Claudia Ouschan and her colleagues at the university decided to look for a way to monitor the long-term levels of glucocorticoids.
As the hormones are known to be present in hair, at least in humans, Ouschan reasoned that measuring glucocorticoid concentrations in dog hair might represent a way of diagnosing Cushing’s disease without causing the animals unnecessary distress.
She thus compared the levels of cortisol, corticosterone and cortisone in the hair of 12 dogs with hyperadrenocorticism and 10 healthy dogs.
The results were striking: all three hormones were found at far higher levels in the hair of dogs with Cushing’s disease than in the control group, with the increase in cortisol particularly pronounced.
The importance of the finding is clear.
“We have shown that the level of cortisol in dogs’ hair is much higher when the animals have hyperadrenocorticism,” Ouschan says.
“Measuring cortisol in hair is so much easier and less painful to the animal than other tests for the disease and we think it has real promise for use as a rapid and non-invasive method to diagnose hyperadrenocorticism.”
The paper, “Measurement of cortisol in dog hair: a noninvasive tool for the diagnosis of hypercortisolism”, by Claudia Ouschan, Alexandra Kuchar and Erich Möstl, is published in the current issue of the journal, Veterinary Dermatology, and is available online at http://onlinelibrary.wiley.com/doi/10.1111/vde.12043/full.