My HRT regimen is an emulation, only simulating the real thing. Cis women experience a complex, month-long dance between estrogen and progesterone, swinging from one to the other and back again. I, on the other hand, experience an estrogen peak every two weeks, and a progesterone peak every quarter.
And that's okay! It's gotten the job done.
Sometimes however, my peaks and troughs happen to look just enough like an actual cis cycle to trigger some fascinating side effects.
This one occurred a few weeks ago. My day started as normal; but something seemed off. I got to work, and began to experience stomach cramps. My first thought was that I must have consumed some disagreeable foodstuff; but this was different - the sensations were prickly; and extended all the way into my pelvis.
It wasn't until lunch time, as I was driving my daughter home from summer school, that it came to me: these were menstrual cramps!
My hormone levels had aligned in such a way that my brain was now sending instructions down my existing nerve pathways to forcefully contract a non-existent uterus...
This state of affairs continued for two days; with what I can only describe as various muscle groups from the top of the abdomen all the way down to the thighs randomly and constantly pinging, eliciting a continuous stream of "Ow! Ow!" noises.
Now: is this exactly what cis women experience? I have no idea. Did the lack of uterus effectively cap the amount of discomfort I felt? Or did it cause the nerve signals to be redirected into other adjacent muscles, making their contractions worse? It's so hard to say.
What I do know is this: I already had a healthy respect for the unpleasantness of menstrual cramps as experienced by others; but this situation made for a very personal window into that world that really reinforced my prior understanding!
Addendum: there is a candy dish in my office that is periodically emptied, and refilled; fortuitously, its contents had been refreshed the day this all went down. My very audible "Oh, thank god!" drew laughter from one of the people that worked nearby and knew what I was going through!