Accepted Answer

There are MANY things that can cause this degree of hair loss in a dog, and we try to differentiate between major categories of them by whether or not the dog is itchy. In the areas where you are describing the hairloss to be occurring, the most common cause is flea infestation. However, most dogs with this significant degree of hair loss over this period of time from fleas, would be very itchy. So, I would say this would be less likely in your dog.
Two diseases that I am concerned about for your dog, that cause hair loss without itchiness are demodicosis and hypothyroidism.
Demodicosis is an infection with a mange mite, that can cause either small or large areas of hair loss. The skin in the affected areas often looks normal and there is no itchiness, as long as there are no secondary bacterial infections present. The vet can easily diagnose this problem with a test called a skin scraping. This is when they scrape a few areas of the dog's skin with a scalpel and then look at the scrapings under a microscope. If the mites are present in large numbers, then you have a diagnosis. This disease is treatable with oral medication, but does take many weeks to resolve.
Hypothyroidism is a disease in which the dog's thyroid gland is underactive and does not produce enough thyroid hormone. This can cause lethargy, hair loss, weight gain, inappetance, etc... This is very easy to diagnose with blood tests (T4, Free T4, and TSH level) and is very easy and cheap to treat with medication.

I am attaching some client information handouts that I use in my practice that discuss some of these conditions in more detail. I hope that you find them useful.

Click Here
Click Here 2
Click Here 3


I hope that this information is of help to you, and I wish you the best of luck with your dog. Please let me know if I can be of further assistance.

Dr. K

Expert:	Dr. K
Pos. Feedback:	100.0 %
Accepts:	343
Answered:	7/21/2008

Veterinarian

8 years experience as Veterinarian