The medial preoptic nucleus is bounded laterally by the lateral preoptic nucleus, and medially by the preoptic periventricular nucleus. It releases gonadotropin-releasing hormone, controls copulation in males, and is larger in males than in females.[WP,unvetted]. [ http://en.wikipedia.org/wiki/Sexually_dimorphic_nucleus http://en.wikipedia.org/wiki/Medial_preoptic_nucleus#Medial_preoptic_nucleus ]