Activation of the HPG Axis at Puberty

• Puberty


  puberty = period of life when the reproductive organs grow to adult size + become functional

  it represents the earliest time that reproduction is possible
• Before Puberty


  b4 puberty, the circulating levels of all steroidal sex hormones (testosterone, oestrogen + progesterone) r low

  even these v low levels r sufficient to suppress secretion of GnRH by the hypothalamus
• Approaching Puberty


  as puberty approaches, the hypothalamus becomes less sensitive to inhibition by these sex hormones

  as a result, it begins to release GnRH in a rhythmic manner

  in resones to the elevated GnRH levels, the anterior pituitary releases FSH + LH

  these gonadtropins, in turn, stimulate the release of more sex hormones from the gonads

  as the threshold for inhibition of GnRH cont to rise, more sex hormones r released until the adult pattern of hormone interaction = achieved

  these high levels of sex hormones bring about the bodywide changes of puberty