TY  - CHAP
M1  - Book, Section
TI  - The Pathophysiological Basis of Androgen Disorders in Men
A1  - Huhtaniemi, Ilpo
A2  - Bhasin, Shalender
A2  - O’Leary, Michael P.
A2  - Basaria, Shehzad S.
PY  - 2021
T2  - Essentials of Men’s Health
AB  - Testicular  production  of  male  sex  hormones  (androgens)  starts  in  the  fetal  period  and  continues  until  the  end  of  life.  Androgens  are  quintessential  for  the  structural  and  functional  differentiation  and  maturation  of  all  aspects  of  the  male  phenotype.  Testosterone  (T)  is  the  most  important  androgen;  some  of  its  actions  require  its  conversion  to  5α-dihydrotestosterone  (DHT)  mainly  in  peripheral  androgen  target  organs.  In  addition,  some  actions  of  T,  such  as  on  the  bone,  brain,  and  sexual  desire,  require  its  conversion  to  the  active  estrogen,  estradiol  (E2).  Normal  testicular  androgen  production  is  critically  dependent  on  regulatory  input  from  the  hypothalamic–pituitary  level  through  the  action  of  luteinizing  hormone  (LH)  and  fine-tuning  by  a  plethora  of  other  hormones  and  intratesticular  paracrine  signals.  Androgen  actions  in  the  testis  and  other  organs  are  mediated  by  the  androgen  receptor  (AR),  a  ligand-activated  nuclear  transcription  factor.  The  pivotal  regulatory  unit  in  androgen  production  is  the  hypothalamic–pituitary–testicular  (HPT)  axis,  where  feed-forward  and  feedback  actions  between  the  hypothalamus,  pituitary,  and  testes  maintain  the  physiological  androgen  homeostasis.  Disturbances  of  this  balance,  leading  to  hypogonadism,  may  occur  at  any  level  of  the  HPT  axis  and  in  AR  function.  The  pathophysiological  basis  of  androgen  disorders  is  localized  somewhere  in  the  cascade  of  androgen  regulation  →  production  →  action,  either  intrinsic  to  the  HPT  function  or  as  a  consequence  of  primarily  nonendocrine  conditions  or  external  influences.  Typical  causes  for  hypogonadism  are  mutations  of  genes  functional  at  the  HPT  axis  (organic  hypogonadism),  consequences  of  nonendocrine  systemic  illness,  or  the  influence  of  exogenous/lifestyle  factors  (functional  hypogonadism).  We  will  first  review  the  normal  processes  of  testicular  androgen  production,  action,  and  regulation  by  the  HPT  axis.  We  then  review  the  pathophysiological  basis  of  the  various  diseases  and  disorders  that  can  disturb  androgen  synthesis  or  action.  
SN  - 
PB  - McGraw Hill
CY  - New York, NY
Y2  - 2024/04/19
UR  - accessmedicine.mhmedical.com/content.aspx?aid=1174514948
ER  -