Just noticed something interesting today. I was taking my shirt off ready for a shower and my left nipple was twitching invonuntarily. Now, I’m assuming it’s just my heartbeat but could it be anything else? If so is it possible for me to do it voluntarily because it’d be a pretty cool party trick 
Rock band name for Jarbaby’s list: Twitching Nipples.
Eh, I dunno, I’d have to guess some kind of small muscle spasm in your pecs. It’d probably be sexist of me to ask whether you’re male or female, so I’ll ask, “Do you have a lot of underlying breast tissue, under the nipple, or are you fairly flat-chested?”
I’m a guy, reasonably flat chested but perhaps a tad more flabby than I should be at my age (18)
P.S. I’m actually in a band and have been looking for a suitable name for ages. Thank you very much for pointing out how damn cool Twitching Nipples is. I promise you , if we ever make it off the lub circuit you’ll get some royalties or something.
Anyway, back to my gyrating man-breast.
Well, I have a fair amount of breast tissue under mine, as well as XX chromosomes, and I’ve never noticed that my nipples are under any sort of conscious control. However, nipples are connected to the autonomous nervous system, which is what raises them when they’re cold. So I suppose you experienced some kind of nerve twitch, or some kind of pectoral muscle twitch, depending on whether it seemed to originate right at the nipple itself, or maybe from deeper underneath.
The reason I asked about the amount of breast tissue mass was because when I flex my pecs (such as they are), not much happens up in the nipple area, as there’s too much “stuff” in the way. The pecs don’t seem to be connected to the nipples at all. So it’s probably a nerve twitch.
And I have no idea whether you need to see a doctor, because a Google search for “twitching nipples” was perfectly useless for GQ purposes, although I did enjoy the trip through the netherworld of the Internet. 
Lotta weeeeeird Earls out there, folks…
It might have been from the temperature change - I have experiened brief and drastic twitches upon clothing removal.
“Twitching Nipple Royalties” would be the coolest memo ever written on a check.
[brief hijack]
In trying to teach my 11 month old how to talk, we’ll walk around the house with her on my arm pointing at stuff and I’ll call out it’s name. Invariable as we walk through the library the two mounted ducks are referenced… “duck, duck…” and I always want to then say “goose”.
[/brief hijack]
It could be your heartbeat. You can see the heartbeat through the chest wall (called the Point of Maximum Impulse-PMI) but normally, I’d expect to see it a little to the left of and below the nipple. If you’ve got some saggy man-breasts though…
Anyway, if you want to check, take your pulse while watching your nipple. If they are in synchrony, there’s your answer.
More likely, I think, is a twitching of a little bundle of muscle fibers. I don’t recall if there are muscle fibers just under the skin in that region (as there are in the face and neck). But if so, a twitch in a superficial muscle should produce the observed effect. Otherwise, you’d need to consider twitching of an isolated segment of your pectoralis major on the left.
Nipples have smooth muscle fibers in them, which are innervated by sympathetic nerves, that can contract and make them poke out. This function has evolved either to aid nursing or to make it easier to tell when someone isn’t wearing a bra.
As far as I know, the only other muscle that will move the nipple (other than a strong heartbeat) is the pectoralis major, which underlies the whole breast region and is separated from the nipple by subcutaneous fat.
If it was just the nipple twitching by itself, it was the smooth muscle fibers. If the whole area was twitching and it wasn’t your heart, it was the pectoralis major. Unless it was cold, I don’t know why. Sometimes muscles just twitch for no apparent reason.
If it’s the smooth muscle of the nipple, you probably can’t do it voluntarily because it’s controlled by sympathetic nerves. The whole pectoralis major is easy to control voluntarily, but sometimes part of a muscle will twitch in a way that you can’t make it do volutarily.
Dude, AFAIK, smooth muscle doesn’t twitch.
That’s true, now that you mention it. Smooth muscle cells are connected in such a way that they all contract at once if they contract. So if someone’s nipple is twitching it isn’t the smooth muscle of the nipple.
It’s a ghost flicking your nipple. 