RT Book, Section
A1 Potts, Jr., John T.
A1 Jüppner, Harald
A2 Jameson, J. Larry
SR Print(0)
ID 1141276831
T1 Disorders of the Parathyroid Gland and Calcium Homeostasis
T2 Harrison's Endocrinology, 4e
YR 2017
FD 2017
PB McGraw-Hill Education
PP New York, NY
SN 9781259835728
LK accessbiomedicalscience.mhmedical.com/content.aspx?aid=1141276831
RD 2024/04/24
AB The  four  parathyroid  glands  are  located  posterior  to  the  thyroid  gland.  They  produce  parathyroid  hormone  (PTH),  which  is  the  primary  regulator  of  calcium  physiology.  PTH  acts  directly  on  bone,  where  it  induces  calcium  release;  on  the  kidney,  where  it  enhances  calcium  reabsorption  in  the  distal  tubules;  and  in  the  proximal  renal  tubules,  where  it  synthesizes  1,25-dihydroxyvitamin  D  (1,25[OH]2D),  a  hormone  that  increases  gastrointestinal  calcium  absorption.  Serum  PTH  levels  are  tightly  regulated  by  a  negative  feedback  loop.  Calcium,  acting  through  the  calcium-sensing  receptor,  and  vitamin  D,  acting  through  its  nuclear  receptor,  reduce  PTH  release  and  synthesis.  Additional  evidence  indicates  that  fibroblast  growth  factor  23  (FGF23),  a  phosphaturic  hormone,  can  suppress  PTH  secretion.  Understanding  the  hormonal  pathways  that  regulate  calcium  levels  and  bone  metabolism  is  essential  for  effective  diagnosis  and  management  of  a  wide  array  of  hyper-  and  hypocalcemic  disorders.