Hi there,
Well..for me my weakness caused by other diseases (ra, thyroid, cancer, heartproblems and so on) was just a different weakness from the mg one. It is like I finally know the feeling of true muscle weakness and muscle fatigue. The other ones gave (give) me more an overall weakness. Like tired-weakness, kind of breakdown weakness.
And MG gives me more, "wtf I can't even chew on this cookie / turn on the page / climb the stairs / breath in weakness. Real muscle weakness, you know: your head to heavy to lift your neck, or a face with no expression.

A doc who is neurologist and endo at the same time? Sounds cool
Nah, I just have a whole bunch of docs, I believe in 3 years Ive seen over 30 specialist probably more.
Well, my thyroid was okay till few weeks ago, my blood says Im hypo again.

Ha, well, how they untangled it? Well, with the first 3 or 4 diseases they just said you are tired / crazy / stressed (the usual). Until they did (after weeks MG even months of begging, because I felt something was wrong) simple lungfunctiontests or bloodtests and i was rushed to the hospital.

It is very MG typical to have weakness one hour, the next hour (when you have your appointment) it is gone! I never experienced this with other weaknesses, so maybe thats useful?

Good luck!