Sex-Dependent GH Secretory Profiles

In many species, the pituitary gland secretes GH into plasma in a highly regulated temporal fashion that differs between males and females. This sex-dependent secretion of GH is most striking in rodents , but key features are conserved in humans . In the rat, GH is secreted by the pituitary gland in adult males in an intermittent, or 

A GH Pulse Induction oiCYPlCll Pulse Frequency Dependence 

GH pattern. GH suppression is also a key determinant of the lower responsiveness of female rats to phenobarbital induction of CYP2B1 (refs 

The response of the class 11 male P450 genes to hypophysectomy of female rats, which derepresses, that is, increases liver enzyme levels to near-normal intact male liver levels, demonstrates that the class II male liver P450s are subject to negative pituitary regulation in female rat liver, where their expression is strongly repressed by the near continuous pattern of plasma GH exposure. These patterns of hormonal regulation are summarized in Table 9.2, which presents the responses of representative sex-specific liver CYPs to continuous and intermittent GH treatment applied to intact, hypo-physectomized and neonatal MSG-treated rats. 

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