Losing hair

Hi,

first of all, english is not my native language, so please excuse all the mistakes I might make here.  
We've been noticing for about two years now that our dog (America Staffordshire Terrier, 6 years old, male, neutered) is losing slowly but constantly hair on his head and neck. The hair seems to be miniaturizing until there's nothing left of the follicle. So very similar to the male pattern baldness actually. We've been to the vet and so far our dog has been tested for abnormal thyroid values, cushing syndrome, a biopsy has been made to test for parasites. Everything came out negative and the vet told us it's most likely a genetic disorder then and we can't do anything about it. Maybe anyone here has seen this sort of hair loss yet and can provide some help?

Here are two pictures of it: imgur.com/a/nKome (can't post the full link yet, since I'm a new member)

Hmm see what you mean, it's not like full alopecia but a real thinning of the hair !

Will have a think and a look around as it's not something I've come across before.

cant see the pic hopefully someone will be along shortly with advice

can I ask what colour your AmStaff is?