Diabetes and Cushing's - chicken/egg question.

Re: Diabetes and Cushing's - chicken/egg question.

Julian Earl — Thu, 24 Mar 2011 17:28:17 GMT

Mr Petrie has very kindly replied now and his opnion is that there is always a dose of insulin to which a dog will respond; once you have some degree of stabilisation of the diabetic status, if the insulin dose is in the high (i.e. resistance) range, then assess the possibility of Cushing's. Testing for Cushing's in a uncontrolled diabetic will indeed have the risk of a false positive result especially if the dog is in the early stages.

Re: Diabetes and Cushing's - chicken/egg question.

Mark Norcott — Thu, 24 Mar 2011 15:55:58 GMT

I don't have it to hand but I wonder if this article may help from JSAP December 2010:

Retrospective evaluation of the effect of trilostane on insulin requirement and fructosamine concentration in eight diabetic dogs with hyperadrenocorticism (pages 642–648)

G. McLauchlan, C. Knottenbelt, M. Augusto, J. Helm, Y. McGrotty and I. Ramsey

Re: Diabetes and Cushing's - chicken/egg question.

Martin Jones — Wed, 23 Mar 2011 14:12:15 GMT

[quote user="robloxley"]

[quote user="Martin Jones"]If things turn out OK, then the Cushings is a lab artefact[/quote]

I'm not sure it's really a lab artefact, maybe more an 'artefact' of measuring cortisol levels in an animal with another, 'stressful' illness.

[/quote]

I really mean that whilst the cortisol response is a true enough event, the label of 'Cushings' is misapplied; artefact is perhaps the wrong word to use. I don't think there's any evidence that the additional stress of DM, whether as a type 1 in its own right, or secondary to insulin resistance in Cushings, is summative - so my flawed logic has been that if the former, then the acth stim response whould reduce; if the latter, it will be unchanged, or else increased as the condition has progressed. Whichever. For most of these, though, it's not till a few months down the line that the Cushings theory really makes its big entrance.

Re: Diabetes and Cushing's - chicken/egg question.

Rob Loxley — Tue, 22 Mar 2011 00:41:04 GMT

[quote user="Martin Jones"]If things turn out OK, then the Cushings is a lab artefact[/quote]

I'm not sure it's really a lab artefact, maybe more an 'artefact' of measuring cortisol levels in an animal with another, 'stressful' illness.

[quote user="Martin Jones"]if things turn difficult, repeating the test might give some degree of quantitative result in that a false positive with DM is likely to have decreased with partial therapy, but a genuine cushings will be unchanged or increased[/quote]

Not sure this has been shown to be the case, though likewise I don't know it isn't. But I'd agree that if there is a suspicion of cushing's, high ACTH stim or LDDST and the DM isn't coming under control then that's probably the time to get the vetoryl out.

Re: Diabetes and Cushing's - chicken/egg question.

Martin Jones — Mon, 21 Mar 2011 21:12:25 GMT

Time to (yet again) make an arse of myself.

Given the false positives on acth-stim with DM, I've always taken the view that if cushings IS suspected at the start (although most of them seem to just become apparent with continuing and frustrated efforts to stabilise the DM), to do an ACTH stim, but if positive then to just carry on and stabilise the DM as well as possible. If things turn out OK, then the Cushings is a lab artefact; if things turn difficult, repeating the test might give some degree of quantitative result in that a false positive with DM is likely to have decreased with partial therapy, but a genuine cushings will be unchanged or increased.

Or perhaps not, as the bigger boys and girls may opine.

Re: Diabetes and Cushing's - chicken/egg question.

Alex Gough — Mon, 21 Mar 2011 15:48:09 GMT

I agree, try to stabilise diabetes first then repeat Cushing's tests, because there will be a lot of false positives on ACTH and LDDST. Careful examination of adrenals on ultrasound may help with diagnosis. However, in dogs with suspected Cushings and DM, the diagnosis of DM is usually pretty certain, while the diagnosis of the Cushings is usually uncertain. You can therefore treat the DM with insulin with confidence, but potentially treating the uncertain Cushing's with trilostane could be harmful if it isnt actually Cushingoid, and can also really screw up further diagnostics.

Alex

Re: Diabetes and Cushing's - chicken/egg question.

Rob Loxley — Mon, 21 Mar 2011 13:46:21 GMT

This has come up a few times here and the consensus seems to be to treat the diabetes first, and if poor control then address the possibility of cushing's. I'd concur with the difficulty of diagnosing cushing's in an uncontrolled diabetic (as it is chronically stressed), and have indeed found false +ve LDDST, UCCR and ACTH stim results in dogs diagnosed with diabetes that controlled simply on standard doses of insulin.