hair loss excessive shedding

Question
our 10 year old neutered labrador retriever is losing hair by the handfull on both sides where his hind legs meet his belly.  He is not scratching and does not appear too be unhappy or unwell.  

Although he sheds hair generously throughout the year it has never before come out in such large compact clumps.

What is this?  and what should we do about it?

Answer
There are many reasons for hair loss, but if it is coming out on both sides and the dog is not scratching it out, I would have the dog's thyroid hormone levels checked to see if he is hypothyroid. Also, even though he is neutered, the adrenal gland makes testosterone in the absence of a testicle.  At his age, the secretions from the adrenal start to fall off and there could be a hormone related problem where he will require extra testosterone to keep his hair and skin normal.  The only way to know that is to ask your vet to test the levels.