fur discoloration

Question
My mom has a toy poodle that is about ten years old and is on medication for thyroid condition and epilepsy. She has recently noticed a darkening of the fur on the dog's back which used to be very light gray. She was wondering if this dicoloration was caused by the medicine.

Answer
Hello Richard,
Actually, the Thyroid medication that your dog is taking is most likely the cause of your mom's dogs hair color change.  I have heard of other dogs on thyroid meds having changes in their hair color.  Hair color changes can also be caused by a number of other things, such as the dog getting an injury at the site of the hair color change, or sometimes if the dog has two different colored parents the hair will change color (but this usually happens earlier in age than 10).  
If you are unsure, you can contact your Vet, and if he is unsure you can have him do a skin test to make sure that there is nothing going on in your mom's dogs skin, but I am almost sure that it is caused by the medicine.  

I hope this helps you some.
If you have other questions, please feel free to ask.

Thanks for using AllExperts.com,
Kim