Lupron and Zytiga side effects

In July we learned my husband has BCR 1 year post prostatectomy. Imaging confirmed 2 small tumors in the prostate bed. We're so surprised given great surgical outcome; cancer contained and surgical margins clear. But, here we are.
Decision to do 18-24 months Lupron injections along with Zytiga/prednisone. First injection was 3 1/2 weeks ago with Zytiga starting a few days later. Until yesterday he was side effect free, none. Then awake all night the last 2 nights. Freezing cold, then hot. Then joint pain. Slept all day yesterday. Now still incredibly tired and sleeping again. The nurses said the symptoms often kick in at the 1 month mark. Question, do these last the entire time on the medication? Or will they diminish? In the next week or so he'll start 20 days of radiation which we know will make him tired. He's not sure he can do this. The good thing is the PSA done on Monday dropped to 0.04 from .25 a month ago. Thanks for any advice.