Sudden ferret agression

Question
I adopted 2 ferrets about a year ago from a rescue.  They were brought to the rescue together, have been together ever since.  Both are males and about 4yrs old.  They have always gotten along together very well, except for about the last 2 weeks.  One has been showing some severe agression to the other.  He bites him mercilessly until I move him into a cat carrier for about an hour then he's fine.  They both get run of the house for several hours a day, nothing has changed in that respect.  We feed the same food the shelter did, haven't changed litter.  I can't think of anything that has recently changed with them.  Neither one every bites us, the one just bites the other.  The poor thing screams so loud I can hear him from upstairs.  Physically he doesn't seem to be sick.  I'm just wondering if there's any reason he all of a sudden started this.

Answer
The most common reason for sudden aggression in ferrets is Adrenal disease which means a trip to the vet to find out for sure.  If I tried to give you some solutions and it is adrenal, they wouldn't help you at all.  So, schedule a vet visit.  Adrenal will probably require surgery and then the hormone levels should go back to normal and the fighting should stop.