On my grandfathers death certificate it says adult failure to thrive. My grandfather did give up once he knew he was going to die from his asbestosis. He had hard time breathing and unexplained weight loss. Why wouldn't the doctor who signed the death certificate put that his adult failure to thrive was due to asbestosis plural plaques disease.

Does it really matter ? Normally cause of death is general, unless more specific required.

This is under "law" is there a law suit or other reason ? If so, family can hire medical examiner to further exam. But I would assume medical condition of person properly documented

Assuming that he was elderly, all I can say is my own experience: both parents' 'cause of death' was really just whatever the coroner felt like putting based on what their medical records showed most recently. In fact it was done over the phone, without even a look at their bodies.
Many list 2 or even 3 causes of death, when it's a matter of disease especially. The first is primary and the others are secondary, etc.

Now if your grandfather lived in an area where asbestos lawsuits are pending, then maybe the doctor didn't want to be involved (or worse). But it's also possible that it was the correct diagnosis, if your granddad really had more time to live but wouldn't eat. Unless you want to hire a lawyer, and have a reason to do so, then there is nothing you can do.

adult failure to thrive was due to asbestosis plural plaques disease.

He was probably considered palliative and all vital organs were shutting down, his lungs unable to function properly. They don't go into specifics in a death such as this.

I would like to know why this is in the legal forum. Is there a reason for that? Do you have a legal question based on your grandfathers death and the cause?

Adult failure to thrive was the actual cause of death. His diagnosis of asbestosis plural plaques disease was a diagnosis that precipitated his death but was not the actual cause of his death.

I am so very sorry for your loss.

The grandfather may have had other diseases, not related to the asbestosis that contributed equally or even more so to his failure to thrive and death. The Dr. may have determined that it was too close to call. If there are a lot of asbestosis cases litigated in your area, the Dr. may have been affected by possibility of having to testify, as joy alluded to. If an asbestosis lawsuit is a possibility, you or the next of kin/executor should talk to one of the hundreds of law firms who specialize in those lawsuits and who will talk to you (or other responsible party) at no charge, most likely.
Depending on how much time has passed, the lawyers may have suggestions of the best course of action. It could be worse, at least the Dr. did not list another (non-asbestosis) cause for failure to thrive.