I think prednisone is known to mess with the menstrual cycle.

"Long-term effects have included HPA suppression, Cushingoid appearance, hirsutism or virilism, impotence, and menstrual irregularities, peptic ulcer disease, cataracts and increased intraocular pressure/glaucoma, myopathy, osteoporosis, and vertebral compression fractures."

From: http://www.drugs.com/sfx/prednisone-side-effects.html

Absolutely! I thought I was entering menopause, but I have been off Prednisone now for couple of month and I am back to normal!

Defnitely the same for me as well. I was on CellCept for 8mos and had nightly nightsweats and no periods. When I stopped - I had a period - but they are erratic for sure - likely due to the prednisone.
Good luck
Nicole

Thank you so much for your responses

Wow - with the menopausal symptoms people seem to be getting while on prednisone, I wonder if it lowers levels of progesterone?

Good question

Have any of you experienced changes in symptoms around the time of your cycle?

TrystynB, I get much, much sicker right before my period.

I always seemed to have more problems around my wife's period too ;-)

I too have had a really irregular cycle since I got diagnosed...I've asked multiple doctors and nurses if it's a side effect of the Prednisone and they all say no! But I think it is. Also, my MG symptoms get worse right before my period. In fact, the two times during the fall that I went to the emergency room for crisis happened...four days before my period. Ha, I'm turning into a cartoon of everyone's worst nightmare about adolescence. Sigh. Because the only thing better than being hooked up to a ventilator is having the nurse outfit me with a huge hospital-issued pad while I'm hooked up to a ventilator.

Russ, you're such a card!

My symptoms get much worse right before my period also.

My symptoms are much more pronounced right before my period, about 2-3 days before, and I need to take Mestinon more frequently.

I had severe bleeding so I had an endometrial ablation and no longer have a period (best decision of my life!). But I still get the hormonal and sometimes emotional side. And now that I think about it I think that I do get worse around that time. I never really put it together because what I usually get is breast tenderness and emotional stuff etc. Good point.

It's good to read all your responses here, since my doctors evidently were not very helpful in answering my menstruation-related questions. It's good to know that I'm not alone, or that I haven't spontaneously gone into early menopause! Thanks ladies. (And Russ. Haha! :)