Hair loss in dogs

[dollyanna]

Earlier this year my 11 year old (who has always had a thick, dense coat) started losing hair - back end, tail, chest and neck areas. Chest and hindquarters were more or less bald. His skin colour also changed in the space of weeks from mostly pink with black spots to almost totally black. At the same time he was drinking a lot - 4-5 times normal - panting a lot and somewhat lethargic.
Took him to the vets who agreed it sounded very cushings-y. Started with simple blood tests and urine as cushings tests are slightly less simple and not straightforward anyway. Normal tests all came back clear, good to excellent for his age. Due to a ery busy patch at work it was a couple of weeks before I could get back to discuss further tests, and in that time he spontaneously recovered almost fully - stopped drinking, energy perked up again, and most of the hair grew back, just thinner around his collar and back end. Even the skin changed back to mostly pink and dark brown spots, literally day by day.
Fast forward 3-4 months and the hair loss seems to be creeping back. No other symptoms as yet. No change in diet, no stress, nothing else.
Cushings doesn't tend to spontaneously resolve as far as we are aware, but we are stumped as to the cause of the hair loss and skin discolouration. It is quite profound - a friend noticed it from a photo on fb.
Does anyone know of any other causes of hair loss, with or without the other possible symptoms? Would just like to gather ideas so I can discuss things with the vet, at the moment it is just hair and not a rapid change but we are monitoring closely - he is at the vet regularly for other reasons anyway.

 

[PucciNPoni]

It is my understanding that cushings doesn't always turn up on the first test, and further tests (there are a few different types of blood panels - think there is one called a ACTH stim which I think only one lab does?) It does sound like the symptoms are presenting themselves.

Other than that thyroid will often present hair loss, allergies can too, but I don't think it gives the blackened skin.

 

[Aru]

Id recheck basic bloods and run a thyroid panel at this point .. oh and a skin scrape just in case...may seem obvious but never any harm to check for passengers as the likes of a flea allergy can do this(only takes one bite)or a demodex issue esp in a dog that is getting older and may be immunosupressed.

There are also a few seasonal hormonal changes possible in dogs..lose in summer back in winter.. but these are much less common then hypothroidism or cushings parasites etc..