Amanda Bynes -- Too Ill For Release ... Doctors Get Extension

Amanda Bynes is in such bad shape ... her doctors secretly got an order from a judge that allows them to hold her for another month ... TMZ has learned.

We've learned Amanda's doctors asked a judge Monday for a 30-day extension to her involuntary commitment. She's been in a psychiatric facility for the last 17 days, and if an extension wasn't granted she would have walked out the front door yesterday.

But Amanda's shrinks made a convincing case ... she is "very ill" and in no shape to care for herself. The judge agreed to the extension.

What's unclear ... whether Amanda's parents will go back to court to regain a conservatorship over her. Initially we were told they would seek another conservatorship, but our sources say they've had a change of heart. Amanda feels betrayed by them for having her committed, so controlling her would be a Herculean effort.

The likely scenario is that the psychiatric hold will be extended for a long time.