Studies in Prok2 receptor mutant mice and Prok2-/-mice showed olfactory bulb defects and disrupted GnRH neuron migration, resulting in a dramatic decrease in the GnRH neuron population in the hypothalamus as well as hypogonadotropic hypogonadism development [43,44]. The gene discussed is GNRH1; the disease is hypogonadotropic hypogonadism.