There seems to be pineal dysfunction in PD...

Increased pineal Fdopa uptake is related to severity of Parkinson's disease - A PET study:

http://pt.wkhealth.com/pt/re/jpin/ab...195628!8091!-1

Serotonin metabolism is regulated by pineal melatonin, and the secretory activity of the pineal gland may be diminished in PD.

Bright light therapy suppresses pineal melatonin synthesis and secretion. It probably affects serotonin metabolism.

http://www.sciencedirect.com/science...d2dd180473a46c