Does radiotherapy cause brain fog?

Yes, it's hard though, because everyone else just expects me to be back to my old normal self. I've completely lost my mojo for work, am trying to wind things back and look after my health, and no-one apart from my partner (and you guys!) understand. I was trying to discuss with my boss that the hormone therapy may be difficult until my body adjusts, and in response to me saying that weight gain is a possible side effect, advised me to increase exercising (noting I already exercise a lot). After all, he goes for a run and immediately loses half a kilo!