Updated: Jul 10, 2018
Kyan Lynch, MD, MA
Queer Health Question: If a trans man has persistent menstrual bleeding 3 months into testosterone what are possible causes?
This question is best answered in two parts:
1) What effects does testosterone have on the body, and when do those effects typically show up?
2) How does testosterone therapy impact monthly bleeding?
Let's start with part 1.
Take a look at this chart, borrowed from the Endocrine Society Guidelines, which shows the effects of T, and when they generally take place.
This chart was created based on observations that researchers made when watching for effects in some people taking testosterone. They shouldn't be considered absolutely true for everyone. Every body is different, and is going to respond a little differently to testosterone. However, this chart does give you a general idea of when to expect what.
As you can tell from the chart, monthly bleeding usually stops (cessation of menses) sometime between 1 and 6 months on T. In fact, in this case, that was true for 90% of trans guys studied. So, likely no reason to stress about it at 3 months, though I definitely relate to wanting it gone sooner! If you are concerned about your bleeding, because it is heavy or you just really hate it, it's a good idea to see a provider who specializes in ovaries and uteruses. There are even some medications, in addition to testosterone, which can help stop monthly bleeding for good. (Want to know more about these meds? Let us know!)
Now, on to part 2.
If we understand how and why testosterone impacts monthly bleeding, we'll know why monthly bleeding stops, and why it might make a comeback.
First things first: why does monthly bleeding happen in the first place?
Basically, between the first and second week of a given menstrual cycle, the ovaries produce a bunch of estrogen, which essentially kicks one egg out of the ovarian nest, sending it hurtling towards the uterus by way of the fallopian tube, where it may or may not meet up with sperm to make a baby. At the same time, that estrogen is also telling the uterus to build up a nice cozy bed of blood vessels and tissue, so that the potential baby will be comfortable settling in for the long haul.
Once that egg is well on its way, the ovaries pull a lever and stop making so much estrogen, and start pumping out progesterone. Progesterone is a helpfully named hormone. Pro= good, more, encourage, and gest- = carry, bear. So progesterone's mission is to get the uterus in tip-top shape for carrying a baby.
If there's no sperm in the picture, all of this was basically done for nothing. If that's the case, the ovaries stop making estrogen and progesterone. Once these hormones are gone, nobody is telling the uterus to keep all that blood and tissue around for a baby, so it just lets it all go. Hence, monthly bleeding.
So what happens when we add testosterone to the mix?
Well, before I can answer that question, I have to make a confession. I left out a key part. Up to this point, I made it seem as though the ovaries are calling all the shots. Not so. In fact, the brain, via the pituitary gland (yes, of prolactin fame!) tells the ovaries what to do.
Many large studies have shown that testosterone therapy reduces the number of hormone messengers sent by the pituitary to the ovaries to get all that menstrual machinery up and running (Irwig, 2017). Fewer messengers = less estrogen. Less estrogen = fewer, and possibly zero, periods.
Moreover, there is some evidence to suggest that testosterone even talks directly to the uterus, telling it to stop it with all that blood vessel and tissue collection (Carwell and Roberts, 2017). The research is a little mixed on this, though.
So, why does it take some time for monthly bleeding to go away? And why might it come back sometimes?
Well, first, you've got to build up enough testosterone in the blood to get the pituitary to stop sending so many messages to the ovaries. This takes time.
Second, all of this hormone messenger business is pretty complex stuff. It's not as simple as flipping an on/off switch. So, occasionally, the pituitary might get enough hormone messengers out to get that ovary pumping again. That's why it is still possible for trans guys to get pregnant when on T.
Lastly, even though T will lead to a lot less estrogen floating around, there still will be some estrogen. That estrogen might keep talking to the uterus behind the testosterone's back, convincing the uterus to stockpile blood vessels and tissue in case another egg is released and fertilized. When that happens, eventually, all of that bloody goop has to go somewhere. Without progesterone to keep it all organized, sometimes it comes out on its own. This bleeding can be referred to as "anovulatory" bleeding, because it's not accompanied by ovulation (aka egg release). It can also be called "breakthrough bleeding" because it's bleeding that occurs outside of the normal cycle.