CASR and vitamin D deficiency: S5, overlay, in yellow) of endogenous Aβ42 (in green) and GABAB1R/CaSR heterodimers (in red), stained by IHC and the proximity ligation assay (PLA), in parathyroid adenomas from PHPT patients with pre-operative vitamin D deficiency compared to normal donors or PHPT patients with replete 25OHD status.