As a result of developing some sort of a sinus condition a month or so after starting to take 6,000 IU of vitamin D3 per day, I eventually started wondering whether there was some connection, and started searching the internet for any indications that there might be one. Well, it turns out that there might be. I made a few posts to my health-related blog (which shows how I've been flailing about for a solution) on this subject, and now it's become apparent that there is a massive disinformation campaign, part of which clearly involves organized Satanism's "grass roots brainwashing" system, designed to hide this connection. In some cases, the same people who push D3 are also trying to steer people away from vaccinations. (I'm not going to touch that subject with a ten-foot pole. All I can say is find a trustworthy medical expert, and good luck with that. Not that it makes much difference, because schools are now requiring students to be vaccinated.)
Besides the highly technical excerpt form a biomedical text which I posted to my blog (not that I understand much of it), one of the few authoritative sources I've found on this subject is an article entitled The Vitamin D3 Scam?, which until I developed a sinus problem and then read the aforementioned biomedical-text excerpt, I would have dismissed as anti-D3 propaganda from the medical establishment.
It's too early to say whether stopping my large D3 intake (I still get some in a multivitamin) will cure my sinus condition, and it might be months before my D3 stores are depleted sufficiently to stop suppressing my immune system.