y roid ▁h orm one ▁in ▁response ▁to ▁low ▁calci um ▁levels . ▁P TH ▁plays ▁an ▁important ▁role ▁in ▁reg ulating ▁blood ▁calci um ▁levels ▁by ▁raising ▁the ▁amount ▁of ▁calci um ▁in ▁the ▁blood . ▁Par ath y roid ▁t issue ▁seems ▁to ▁have ▁a ▁low ▁turn - over ▁rate . ▁ ▁Hist ology ▁G astr ic ▁chief ▁cells ▁are ▁ep ith el ial ▁cells ▁which ▁are ▁found ▁within ▁the ▁g astr ic ▁unit ▁or ▁g astr ic ▁g land , ▁and ▁form ▁the ▁base ▁of ▁the ▁g astr ic ▁unit . ▁The ▁g astr ic ▁chief ▁cell ▁has ▁an ▁extensive ▁network ▁of ▁l am ell ar ▁rough ▁end op las mic ▁ret icul um ▁organized ▁around ▁the ▁nucle us . ▁The ▁g astr ic ▁chief ▁cell ▁also ▁contains ▁many ▁large ▁secret ory ▁ves icles ▁filled ▁with ▁dig est ive ▁en zym es ▁in ▁the ▁ap ical ▁cy top las m . ▁ ▁Par ath y roid ▁chief ▁cells ▁make ▁up ▁the ▁majority ▁of ▁the ▁par ath y roid ▁g land ▁along ▁with ▁ad ip ocy tes ▁and ▁o xy ph il ▁cells . ▁Par ath y roid ▁chief ▁cells ▁have ▁large ▁amounts ▁of ▁organ elles ▁associated ▁with ▁protein ▁synth esis . ▁ ▁As ▁in ▁many ▁end ocr ine ▁org ans , ▁with ▁age , ▁more ▁o xy ph il ▁cells ▁appear ▁in ▁the ▁par ath y roid ▁g land . ▁ ▁D ise ases ▁In ▁g astr ic ▁t issue , ▁a ▁loss ▁of ▁par iet al ▁cells ▁due ▁to