Is there meaningful mass production of glucose (or dextrose) from corn? Corn syrup is higher in fructose, which is metabolized very differently from glucose.
Absolutely! The glucose mix initially produced from corn is about 50% glucose and 42% fructose, which is roughly the same ratio as you get from beets or cane. You can then _optionally_ raise the percentage of fructose to 55, 65 or even 90% fructose. The 90% stuff is usually diluted/mixed before use.
HFCS is just sugar syrup with an intentionally elevated level of fructose. There's nothing that specifically ties corn to high amounts of fructose, other than that corn is heavily subsidized in the US while other sources of sugar are hit with import tariffs. So corn is what US sugar producers will tend to use as a source.