a friends dog is losing hair quite dramatically. the old hair is not being replaced by new so he is going bald. vet has checked thyroid which is ok and a hair test said that the hairs are dying off. The vet said they look like a chemotherapy patients hair. Diet is OK. no stress. Vet doesn't have any other ideas.

Has anyone come across anything like this? Dog is 7 year old entire male. Long coated breed.

Hyperadrenocortism is a disease in which the body produces too much cortisol.  Diagnosis of hyperadrenocortism may require a urinalysis and more blood tests than hypothyroid, but the disease can also be controlled with medication and other procedures.

I will mention it as a possibility, but he doesn't have any of the other symptoms is thin rather than fat and the hair loss is generalised rather than on the flanks as one site suggested

Has the Vet done a skin scrape to check for mites or maybe the dog could be allergic to something in the food.  He would need a York blood test to check for allergies though.