I have to agree with Marcia, but should add this. I have let my GSD, Greta, bark at the door when the door bell rings since I brought her home 15 months ago.

My husband trained our last GSD and she was a very very sweet and a no problem at all dog. Since my husband has been extremely busy, I have been training Greta, who has a very different personality than our last dog and I have never trained a dog before. When my granddaughter opened the front door, when Greta was barking at it, and she jumped up and nipped my old neighbor I was shocked!

When I told my husband what happened, this is what he said: You have let her bark at strangers at the front door long enough for her to think that is her job now. You let her get so worked up and into a protection frame of mind without training and/or correction that she thinks it is ok to do now.
Another words, take responsibility for what happened and handle it before something really bad happens.

I think what Sheila meant about GSD's is that even though each dog can have a diffent personality, they usually all are hardwired to be protective and need a job. This is why they need a lot of training, correction and something to do. They are also very intelligent, loyal and loving dogs to their people.

I guess one thing that has also crossed my mind,what if the dog is getting this energy from the OP during these times when the dog has reacted?
I keep thinking of all the times I have watched Cesar Milan, on the Dog Whisperer, Cesar says that the energy from the handler goes directly through the leash to the dog.

It could be possible that after several of these incidents, that the OP has started to fear the dogs reaction and thus making the dog react to her fears.

Dogs are very in tune to their handlers and feed off their energy. Just my thoughts on this any way.

Tanith,
I will know something about Kobe's thyroid function by Monday, but vet said she had not seen many cases of this being the cause of aggression. She was much more hung up about getting Kobe neutered, but I have read many times, including on Ed's web site that this does not help the situation if a dog is past 1 year old. I would have it done if there were any chance that the overload of testaterone is what is going on with him. On one hand she said that the insanity at the door is related to the present behavior, in other words he is now "taking it on the road". then she said that she has 3 neutered dogs who do the same thing. So if his aggression with people is caused by test. but not his ferocity when someone comes to the door, how can they be related?
HOw did you get that beautiful dog's picture on the forum? He/she looks alot like Kobe.
Nancy...

Anna,
does your husband have any suggestions for UNtraining a dog who thinks it is his job to protect us by barking at the door?
Nancy

I think your vet is saying what everyone else here is trying to say:

 Quote: nancy black

...she said that the insanity at the door is related to the present behavior, in other words he is now "taking it on the road".

Back to a training regimen...

Train a replacement behavior.

 Quote: Nancy Black

Anna,
does your husband have any suggestions for UNtraining a dog who thinks it is his job to protect us by barking at the door?
Nancy

I'm not Anna's husband, but my suggestion is to give him another job to do.

 Quote: ana kozlowsky

This does not seem to be such a new problem:

4/10 - 2.5 m GSD Kobe - aggression "out of the blue"

7/07 - 4 yr m GSD
"overprotective"

There is certainly some pattern to this. The previous dog was a half-brother, right?

Good eye, Ana... Nancy, you posted about nearly this exact issue 4 years ago - with your current dog's half brother? IMO, that pretty much reinforces the idea that this particular line of dogs goes through a dramatic maturation period between the ages of 2.5 and 4, and what you're seeing is simply related to adult temperament and training... don't be deterred, you can work through this.

What did you end up doing to work with Kobe's predecessor on this issue?

Also, you are correct that neutering Kobe at this point will probably not change his behavior - once it starts, it's too late to put your hopes on the loss of testosterone changing anything (trust me on this one - been there ). What you need to do is modify your training. It can be done, but you'll need to be absolutely methodical, persistent, and patient. Start today - work on "go lie down". Work on "stay". Once he's solid, when he starts up at the doorbell, direct him to his bed. As many times as you need to to get him to stay, get him to stay on his bed (and praise him when he does!) - all of this can be done correction free, with markers, body blocking and persistence... rinse and repeat...

~Natalya

Joyce,
Caesar is right that a dog gets some signals from the dog's handler and his mental attitude, but that "psychology" does not apply to my situation. the first episode happened when I was not holding Kobe's leash, it was fastened under my chair. I was enjoying my lunch with absolutely no concern that he would take off like he did. The second episode was when husband was on the other end of the leash, and he sure had no foreboding that Kobe would react to a lady holding a baby walking past us. And the third time I was talking to my neighbor's wife and was remiss in not being watchful with Kobe, but I am not used to wondering if he will try to take this person down to the ground. At least I wasn't. Today, even with the muzzle on Kobe, I was a bit apprehensive knowing the vet tech and the vet were going to come in the room where we were waiting. And I knew this whole vet thing was not familiar to Kobe, so what would happen when they came in? He had to have sensed my apprehension as I was holding a tight lead on him for about 30 mins, as vet was "running late".
Would you believe this perfect dog acted like a perfect gentleman, not an ounce of Who are You, What do YOu Want, I Don't Like You, the vet must have thought I was nuts when I told her what has been going on. So that kind of shoots the owner mentality theory out of the ballpark, or it proves that this dog is really a weirdo!
Nancy

 Quote: Nancy Black

... the vet must have thought I was nuts when I told her what has been going on. So that kind of shoots the owner mentality theory out of the ballpark ...

Excellent. Then we can go back to the training topic that has run throughout this thread.

 Quote: Natalya Zahn

Good eye, Ana...

Tammy noticed it first.