It has been demonstrated that a microRNA switch regulates the increase in hypothalamic GnRH production before puberty, thus if this event does not occur accurately it may lead to the loss of GnRH expression or alteration of the rhythm of GnRH release and cause hypogonadotropic hypogonadism and infertility in mice (27). The gene discussed is GNRH1; the disease is hypogonadotropic hypogonadism.