My GP recently thought my thyroid level was too "high" by a tiny amount over the normal and lowered my thyroid replacement dosage. Soon after my worst PD symptom, constipation, and general wearing off got worse to the point that I am in daily agony. I called her and begged to go back on previous dosage. She said OK, try it. I had thyroid cancer and thyroidectomy in 2001, PD appeared in 2002. Anyone else see a relationship between thyroid levels and pd meds effectiveness?