Editing Delayed puberty (section)

=== Genetic or acquired defect of the hormonal pathway of puberty (hypogonadotropic hypogonadism) ===

The [[hypothalamic–pituitary–gonadal axis]] can also be affected at the level of the brain.<ref name=":5" /> The brain does not send its hormonal signals to the gonads (low [[gonadotropin]]s), causing the gonads to never be activated in the first place, resulting in [[hypogonadotropic hypogonadism]].<ref name=":12">{{cite book | vauthors = Pariseai M |date=2008 | chapter =Gynaecological endocrinology | title = Obstetrics and gynaecology |location = St. Louis | publisher = Mosby | isbn = 9780723434726 }}</ref> The HPG axis can be altered in two places, at the hypothalamic or at the pituitary level.<ref name=":12" /> CNS disorders such as childhood brain tumors (''e.g.'' [[craniopharyngioma]], [[prolactinoma]], [[germinoma]], [[glioma]]) can disrupt the communication between the hypothalamus and the pituitary.<ref name=":2" /> Pituitary tumors, especially [[prolactinoma]]s, can increase the level of dopamine causing an inhibiting effect to the HPG axis.<ref name=":3" /> Hypothalamic disorders include [[Prader-Willi syndrome]] and [[Kallmann syndrome]],<ref name=":1" /> but the most common cause of hypogonadotropic hypogonadism is a functional deficiency in the hormone regulator produced by the hypothalamus, [[gonadotropin-releasing hormone|the gonadotropin-releasing hormone]] or GnRH.<ref name=":0" />