My Lab is going bald!

Please Help! My 7 year old chocolate lab is losing his hair! His face is a disaster and has bald spots all over it along with his legs and torso.. the only part that seems to be spared is his tail and rump. I took him to the vet last week and they have no clue what's wrong with him! The took skin scrapings for mange and did not find any mites, he does not have fleas and they took hair samples to look for fungus but that takes 6 weeks to get back...  
Basically they sent me home with 2 types of shampoo to treat him for mange and a months worth of antibiotics to treat him for a viral infection.. I have two toddlers and both my husband and I work all day.. I have rarely seen him scratch or lick but it is possible he is and I just don't see it...he tends to hide once we all get home...His diet has not changed and he is an indoor dog. Any advice on what may be wrong with him?

[Aleda M Cheng, D.V.M., C.V.A]

Your veterinarian was checking to see if your dog has Scabies or Demodex mites, or dermatophytosis (ringworm) or other types of skin fungal infections.  Diagnosis must be established prior to treatment for these conditions since the treatments can have side effects.  Your veterinarian may consider additional tests for the mites including skin biopsies and fecal analysis.

Other common causes of hair loss include Endocrine Disorders, Idiopathic Alopecia, and Seasonal Alopecia.

Endocrine Disorders include Hypothyroid disease and Hyperadrenocortism.  These diseases become more common as a dog ages, and can be diagnosed with blood tests.  Hypothyroid is fairly common in older dogs and is a result of Hashimoto’s Thyroiditis which is an autoimmune disease in which the immune system attacks it’s own thyroid gland.  The disease can be controlled with thyroid medication.  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.

Idiopathic alopecia means hair loss of unknown cause.  Seasonal alopecia may also be an endocrine disorder but is not yet understood.  

The tests for hypothyroid and hyperadrenocorticism may be beneficial, as would the further skin tests in your dog's case.