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My black dog's fur is turning brown and he's losing hair. Why?

Updated On September 23rd, 2025

Pet's info: Dog | Mixed Breed Large (61lb +) | Male | neutered | 11 months and 13 days old | 100 lbs

I have a dog that was solid black and had the softest fur ever and now he's losing hair over his chest/torso area and turning brown. Could this be sunbleached, growing into his adult coat, or thyroid related? I know for sure he's mastiff mix so maybe mastador with a little bit of pitbull terrier but I don't know for sure. Any tips to help this? Has gotten worse since pictures below

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1 Answer

Most Helpful Answer

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Answered By Jeffrey Milner

Veterinarian

Published on June 11th, 2017

Smokey could definitely be experiencing some changes to his coat due to growth. I would certainly suspect this particularly if he is not having any sort of itchiness. Thyroid disease is common in dogs, but very uncommon in younger pups. I don't believe I have ever seen a hypothyroid dog under the age of 6 or 7 years. Sunbleaching can happen but it wouldn't cause actual loss of hair. Hair loss in absence of itching is typically due to something like you have described, an endocrine condition, or some sort of immune mediated condition. As long as the hair loss hasn't been spreading considerably and there are no other clinical signs of illness, I would continue to monitor the situation carefully for a few more days before going to the vet. If there is itchiness associated with the problem, Smokey will likely require some therapy in the form of both topical and systemic drugs. Hope this helps. Let me know if there is anything else I can do to help.

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