PDE5A and hypogonadism: However, a direct role of hypogonadism in HFD-induced PDE5 upregulation was ruled out by the observation that hypogonadotropic hypogonadal rabbits (GnRH analog-treated group), characterized by a reduced plasma testosterone/estradiol ratio, showed prostatic PDE5 mRNA expression similar to that of the RD group, which was not modified by T treatment [97].