Transfems read this thread
Biological anthropologist here: TERFs are dead wrong about estrogen/testosterone not changing the skeleton. They do so much to the skeleton we had to completely reassess one of the ways we estimate the biological sex of skeletons.
So, before the advent of cross-sex hormone therapy, one of the surefire ways to ID a biologically female skeleton of a person who had borne children (this is important) was by looking for pits of parturition. These form when the estrogen surge during late pregnancy tells your pelvic ligaments to loosen up in order to fit the baby’s massive head through the birth canal. Your pelvis starts to s There’s hypothetically only one normally occurring biological reason for a body to give that signal, and since you have to be nominally XX (or some variant of that where you can still carry a pregnancy to term), it was a pretty solid shorthand for sex!
Until we started looking for these things outside of female skeletons, and surprise! “Male” skeletons can have them too! Sometimes these are chromosomal variants, sometimes they’re men with a high estrogen or estrogen-esque hormonal component, and in the modern era? Sometimes these are trans women whose skeletons have undergone hormonal changes due to taking estrogen.
And then there’s testosterone. You know what that does, right. It makes it easier to build muscle. But what THAT does is put new and interesting stresses and pressures on the bones, making them more rugged and in line with the skeletal structure we see in people who have had high testosterone their entire lives. We don’t just see this in trans men- we see this in older cis women too. Once your estrogen production tanks after menopause, we see what we call masculinization of the face, where the features get more rugged and robust as tissue production changes. These changes don’t happen overnight, and we don’t have good data (yet) but my guess is that when we start looking at the skeletal remains of trans men who took T throughout their adult lives, their skulls are gonna look pretty damn masculine.
Now, hormone therapy isn’t going to change every aspect of your skeleton. Estrogen in particular doesn’t do too much to the cranial bones. Your skeletal height and limb length are unlikely to change. Things like the size and shape of the pelvic inlet, the sciatic notch, and other features that are used in sex estimation, are also unlikely to change. Professional anthropological sex estimation is a complex calculus where you look at many, many features of the skeleton to make the best possible estimation of what sex the person was. It has nothing to do with gender or gender presentation. It simply tells us the end result of your hormonal composition during life. So long as you’re taking hormones regularly for a while and giving your body a chance to change and grow, your skeleton WILL undergo changes based on your hormone levels.
Hey, one anth to another: I'd love to read some of this literature, do you have any reccs? Cause I always figured that hormones would change things like bone density and possibly some of the shape, but after fusing and ossification they cant change things like the sciatic notch and the bowl shape of the pelvis and whatnot. Because I know that in grad school we did learn about the pits of partirition but as like an outdated thing that isn't very useful for sex ID anymore (if anyone's wondering, these are the source of that "pregnancy leaves notches on your pelvis" post that was going around tumblr a few years back. It isn't true.). Tho I'd love to see a study on the hands thing the op mentioned. Like I know a lot about the skeleton at this point and I'd love to know how that happened. Was it remodeling? Did the hormones somehow "reactivate" the ephyphesys? Change the bone ossification? Or was it all soft tissue? Because we do know that males and females have different proportions to their fingers vs palms (that's how the handprint paintings in caves were IDd as done by women.), but is it bone or soft tissue? Idk man it's just really interesting.
Yeah! Fair warning, a lot of these papers use terms that the trans community no longer sees as appropriate. The language standards that the medical community uses are not the same as the trans community at large (I’m sure any trans person can tell you that!) so you’ll see terms like “transsexual” a lot.
The TL:DR from all of this: there is good evidence for skeletal changes during adult-initiated HRT. We know that these changes occur, but there isn’t a whole lot of literature about exactly what occurs. Many of these changes are minute and you may not see them in a living trans human, but are more discernible in a skeleton. We need to study this more.
Introductory Stuff
A nice Sapiens article proposing how to improve trans visibility within bioarchaeology/forensics: https://www.sapiens.org/biology/transgender-intersex-forensic-anthropology/
Why it’s important to be able to talk about the bodily changes trans people go through as an anthropologist: https://journals.upress.ufl.edu/fa/article/view/1409
Studies of skeletal development in trans people taking hormones
Bone health as a part of trans healthcare: https://www.sciencedirect.com/science/article/pii/S8756328208007722?casa_token=Q0yyPHewOLIAAAAA:f6VKhwq1uVylVHkVZtAX6c-t3WADx8aaymmIWtiUeci1dqVuYAMH9OXn2ofmm4T1thKw5dkutuw
Hormones and bone density: https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1365-2265.1998.00396.x?casa_token=o2l0Y9Nt4qoAAAAA:tO3_aIeM4RqBE0xyNpC8Ns8d7vipYNFzsdMdaX5ZcodO9JShKdEkh-Vw-66FKJAW13bDG2pCCKKUYeyc
Interesting paper on pelvic morphology changes: https://asbmr.onlinelibrary.wiley.com/doi/full/10.1002/jbmr.4262
(this one’s about people who started HRT before 18, but it’s still a really interesting read even if it isn’t directly applicable to OP’s situation since they transitioned as an adult)
10 year bone health study in transgender individuals: https://asbmr.onlinelibrary.wiley.com/doi/full/10.1002/jbmr.3612
Not hormones, but stuff on how FFS affects skeletal remains: https://pubmed.ncbi.nlm.nih.gov/32200173/
Ok, so we’ve identified that there ARE bone changes. How does muscle affect bone structure?
Explains the bone/muscle relationship in typical cis men and typical cis women: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3189615/ (Note: by typical, we mean that their hormones are generally within the range that’s expected for their chromosomal composition.)
Comparing trans men on long-term HRT to cis women of the same age and looking at bone mass, body composition, etc: https://academic.oup.com/jcem/article/97/7/2503/2834495
Facial masculinization of the female cranium with age: https://digital.library.txstate.edu/bitstream/handle/10877/5250/NAPARSTEK-THESIS-2014.pdf?sequence=1
Cranial remodeling with age: https://onlinelibrary.wiley.com/doi/full/10.1111/joa.12247
(The aging stuff is important because hormonal composition changes drastically with age and it’s a useful analogue, if not direct analogy.)
Some interesting reads on the relationship between sex hormones and cartilage
Estrogen and osteoarthritis (aka cartilage loss): https://www.mdpi.com/1422-0067/23/5/2767/htm
More sex hormones and osteoarthritis: https://faseb.onlinelibrary.wiley.com/doi/abs/10.1096/fasebj.27.1_supplement.1053.15
Generally speaking, HRT isn’t going to do too much to the cartilage. If you think your nose looks different, it’s probably because you’re seeing it in a new context since the fat deposits on your face rearrange themselves. They’re very close to the surface, after all.
Pelvic Scarring and how it’s not strictly based in pregnancy
Oops we found it in men: https://onlinelibrary.wiley.com/doi/10.1002/oa.2887
It’s also found in women who have never given birth: https://digital.library.txstate.edu/bitstream/handle/10877/8481/GALEA-THESIS-2018.pdf?sequence=1
Identifying transgender people within archaeology
https://miami.pure.elsevier.com/en/publications/the-fallacy-of-the-transgender-skeleton (good read on how human sexual dimorphism... isn’t. The spectrum of traits overlaps too much.)
surgery piece: https://www.sciencedirect.com/science/article/pii/S0379073820300827?casa_token=jy_vbV7_fXkAAAAA:nz2d-xCUT-JoYACam3CDliKmto1UFkB8-ft837QzSpjLZJ0uiH5DHNSH7M_fG_b5XWsln3yZZKk
As for the mechanism, it’s a combination of remodeling and changes in bone density. The bones don’t unfuse, so you’re basically stuck with the same structure, just with different sizes and densities. This is more notable in trans men- they can lose some height from bone density loss if they’re not careful. It’s usually not a lot and isn’t as noticeable in living people as it is in skeletons, because there’s a lot more tissue to you than just bone! It’s the same mechanism that happens in cis women with osteoporosis. Fortunately, most endocrinologists take that into consideration these days.
Right now, most of the research on skeletal changes is focusing on FFS because it’s much more visible and dramatic. There’s a lot of reasons we don’t really understand everything that HRT does to the skeleton- we know a lot of it, but not everything- and how any of it shows up in the archaeological record. One of them is that HRT is relatively new and we don’t have the representation in skeletal collections. Another is that most of our standards are written based on studying white people, and while you can’t truly identify race from a skeleton, you can associate a skeleton with certain genetic groups based on suites of traits. By only including white skeletons in a study, you miss out on a TON of variation.
I know this is a little disjointed, but I think it’ll help as a starting place for people interested in doing more research on the relationship between HRT and the human skeleton and how we can see some of these changes in the archaeological or forensic context!
Amazing list of resources, and as a biologist in training imma take a dive into these.
But a friendly reminder: the key ingredient of HRT is PATIENCE. I've already read a lot of studies, and most seem inconclusive, but all agree on one thing: time on HRT (with appropriate levels) supercedes the majority of other factors involved with feminization/masculinization. Don't let someone tell you you're "done" at one year, two years, five years.... this is lifelong. Your body will adapt to the hormones it currently has at the age it is. Let it do that, and give it the time to do so.
