The panel obviously want more information which is why they have requested your medical records, but this may still not be enough to override their concerns. Understand, they can remove points that you already have, this could lead to a reduction in award or even it's complete removal.
If you decide to withdraw your appeal then just contact the Tribunal Service, you will need your appeal reference number, it can be done over the phone if it easier.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems