It can happen, but not having a period in the absence of pregnancy is not a serious thing, unless you are trying to get pregnant! I used to have amenorrhea when I was younger and the general rule was to "see about it" after 6 months or so of no period. The gyno will likely only give you hormones to induce a bleed, and the hormones of course have the potential to aggravate the MG. If you are in your mid-late 40's you could be peri-menopausal and missed cycles are also common.

It's funny how neuros just don't want to get involved with anything having to do with anything other than the MG! Once I mentioned I was having lots of migraines to my MG neuro, and she told me to see a neuro! LOL