We present the case of a 59-year-old male with a history of type 2 diabetes mellitus, hypertension, hyperlipidemia, and prostate cancer who developed intractable headache, nausea, vomiting, photophobia, and blurred vision shortly after receiving a leuprolide, GnRH agonist injection, for the treatment of prostate cancer. Here, GNRH1 is linked to diabetes mellitus.