Parkinson Disease & Thyroid Cancer

Is there anyone out there with Parkinson Disease and a survivor of Thyroid Cancer.  My sister is struggling with her Parkinson Disease even after going through Deep Brain Stimulation Surgery over 1-1/2 years ago.  She is 68 years old.  She and I wonder if her struggle has been so difficult because of the removal of her Thyroid.  She takes Synthroid every day but even that must be watched because of levels too high or too low.  Another problem is the company which made her Sinemet has changed its Vendor and the Vendor is not using the same composition.  Her medication that once had a coating on it now has none and it disolves as it touches her tongue.