To quantitate the impact of vitamin D deficiency on signaling cascades of APP/Aβ and the GABAB1R/CaSR heterodimer, we compared parathyroid cell-defined proteomic profiles in the parathyroid tissue of normal donors and in adenomas from PHPT patients with deficient (<20 ng/ml) or replete (>30 ng/ml) pre-operative 25OH vitamin D levels. The gene discussed is APP; the disease is adenoma.