RT Book, Section
A1 Grimberg, Adda
A1 DiMeglio, Linda A.
A2 Kline, Mark W.
SR Print(0)
ID 1182918332
T1 Mechanisms of Hormone Action
T2 Rudolph's Pediatrics, 23e
YR 2018
FD 2018
PB McGraw-Hill Education
PP New York, NY
SN 9781259588594
LK accesspediatrics.mhmedical.com/content.aspx?aid=1182918332
RD 2024/04/19
AB Hormones  are  molecules  secreted  into  the  circulation  to  influence  the  function  of  target  cells  in  another  tissue  or  organ.  In  addition  to  distant  targets  via  the  circulation  (endocrine  action),  many  hormones  also  influence  the  function  of  the  cells  that  secreted  them  (autocrine  action)  or  that  of  adjacent  cells  (paracrine  action).  For  example,  when  insulin,  produced  by  pancreatic  beta  cells,  stimulates  glucose  storage  and  oxidation,  protein  synthesis,  and  lipid  storage  in  the  liver,  muscle,  and  fat,  it  is  acting  in  an  endocrine  fashion;  when  it  inhibits  glucagon  secretion  by  the  nearby  pancreatic  alpha  cells,  it  is  acting  in  a  paracrine  fashion.  Frequently,  the  endocrine  and  autocrine/paracrine  actions  of  a  hormone  lead  to  the  same  effect.  For  example,  growth  hormone  (GH)  stimulates  hepatic  production  of  insulin-like  growth  factor  I  (IGF-I),  the  main  mediator  of  somatic  growth  in  childhood.  Mice  with  targeted  hepatic  deletion  of  IGF-I  expression  grow  to  normal  size,  despite  a  75%  reduction  in  circulating  IGF-I  concentrations.  This  seminal  experiment  demonstrated  the  importance  of  autocrine  and  paracrine  IGF-I  production  by  other  tissues  to  body  growth.