Answer

Hello and thanks for researching this very important question!

Flea bite inflammation can cause fur loss and skin damage that takes some time to heal, but if your pet was not observed actually chewing at this skin until it bled (and thus down past the hair follicles), it seems to me that something else may be going on.

Very observant human companions can sometimes catch a medical issue in a very early stage.

Far and away the most common cause of thinning hair (and eventual balding) in Golden Retrievers is low thyroid function (Hypothyroid)....either from primary thyroid failure, or from an autoimmune condition that attacks the thyroid and destroys it over time.

Symptoms can include weight gain, thinning and/or brittle hair coat, thickening and darkening skin patches, cold intollerance, and weakness, depending on how severe the hormone shortage is and how sensitive owners might be to changes in their pets. Goldens are particularly noted for developing a "rat" tail...the feathers shed and the entire tail can become bald in time. Strangely enough, a balding letter "H" (for Hypothroid?) can appear at the root of the tail with many of these patients!

Hypothyroid produces many more sickly symptoms as time passes...thyroid hormones work throughout the entire body, including the heart and brain, so replacement or thyroid hormone is really really important when a pet is diagnosed as "low"!

The thyroid glands are part of the Endocrine system, and sometimes problems in other glands can adversely affect thyroid function.

An exhaustive list of things that can cause hair loss in dogs is included here: Read Information.

Since hypothyroid is so common, and can cause so many other health problems, I would definitely have her re-checked and evaluated for this condition.

Here is an article written by veterinarians that discusses tests to perform diagnostically:
http://www.veterinarypartner.com/Content.plx?A=461

And an article published by a private veterinary clinic:
http://www.newmanveterinary.com/Hypothyroid.html

Article by the Golden Retriever Club of America: Read Here.

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