Will it ever grow back????

Question
I wish I had found this site two years ago!
Living in Texas where the summers are really hot and humid, I
thought my pom would appreciate having a summer cut. I asked
the groomer if his hair would grow back and she assured me it
would. It was cut to about an inch all over.
He had a HUGE coat before - Lots of undercoat, lots and lots of
top coat. Now, TWO YEARS LATER, the undercoat has grown
back but the top coat has just barely started to come back. UGH.
In some ways maybe its a blessing that for the summer his coat
is still thin.
Maybe it's because it's so hot here that it's not growing back?
Is there anything I can do to help his coat come back in?
supplements? How long do you think it will take before it will
grow back?
There are a lot - in fact most - of the poms here are what I call
"southern bred" meaning they have only a single coat. When
their coats are cut/shaved/trimmed for the summer they grow
back quickly and look the same. I've not seen another pom here
that has a coat like my dog's that has been cut or trimmed. (He's
from a long line of champions.) Please, tell me it will grow back!
Thanks.

Answer
There are many reasons why a Pom does not grow back their
coats.  In this case, you will need your vet to run some
tests for Thyroid, mange mites, etc.  Our breed depending
of the bloodlines has a major problem call BSD which mean
Black Skin Disease and coat loss.  Again a vet will have to
test for these conditions.

In the meantime feed him good quality food that you buy from a pet store (not grocery store quality) and find some
Salmon oil to add to his kibble.