I remember well the profound fatigue and feeling of being cold my husband experienced as beginning symptoms of PD. At the time I wondered if the fatigue was due to mitochondrial dysfunction and if the lack of body warmth was due to mt dysfunction also, or if it was a manifestation of autonomic nervous system dysfunction. Seems a small percentage of ATP produced is utilized for thermal regulation--ie to maintain body warmth. Initially, the use of megadoses of CoEnzyme Q 10 helped with both of these symptoms, though both symptoms have re-occurred.