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Table 1 Here proposed different settings of leptin and GnRH actions during different phases of growth and aging and in anorexia nervosa

From: A phase plane graph based model of the ovulatory cycle lacking the "positive feedback" phenomenon

Phases of growth & aging

GnRH rhythm and GnRHR availability

 

Leptin

GnRH

Female

Male

Children

low

secretion

minimal secretion

 
  

receptors

normal or increased pituitary receptors

 

Early pubertal

normal

secretion

intermediate secretion

 
  

receptors

normal pituitary receptors

 

Healthy adult

normal

secretion

low secretion from lutheolysis through follicular phase till the preovuatory days

stable

   

high secretion from preovulatory days till lutheolysis

 
  

receptors

slowly up-regulated pituitary receptors during preovulatory days due to low GnRH exposure

stable

   

rapid downregulation of pituitary receptors during the ovulatory surge due to GnRH overexposure

 

Healthy postmenopausal women

normal

secretion

low secretion due to estrogen deprivation

not applicable

  

receptors

increased pituitary receptors due to low GnRH exposure leading to high FSH and LH secretion

 

Anorexia nervosa

low

secretion

minimal secretion

 
  

receptors

normal or increased pituitary receptors

 
  1. It is important to note that shifts in GnRH secretion are expected only in women, they happen in lutheolysis and preovulatory and are compensated by changes in the availability of GnRH receptors within the following days. This might explain the unique susceptibility to downregulation of the GnRH pituitary receptors.