On the Science of Changing Sex

Biological Reality! Transsexual Women’s Breasts Are Female Breasts

Posted in Transsexual Field Studies by Kay Brown on May 19, 2022
Kay Brown with her adopted daughter Liz

Yesterday, a post about a transwoman breastfeeding a baby went viral. As one could imagine, transphobic commentators had many nasty, ugly comments to make. However, it also became clear that they were under the misapprehension that transwomen couldn’t breastfeed, “Your male body can’t produce milk!” “You don’t have female breasts.” “Where is the colostrum?” “Where are the lobules?” Why do they object to this knowledge and go into deep denial? Could it be because of their reliance on an ugly propaganda slogan of “biological reality” which they say transsexuals are in denial of… yet, here is something that they claim can’t be done, a true female biological function that can only be performed by women, by only natal female women, that is being done by transwomen. Learning that transwomen can and do perform this uniquely female, womanly function of sharing life giving milk with a baby upsets their world view and their propaganda.

So, sad as the need to explain such basics of mammalian biology to the world is, it must be done, as these ignorant and false assertions from these transphobes proves.

First, it important to understand that each and every gene that a woman has is also found in males. Females have two copies of the X chromosome while males have only one. But they still have that one. Further, many of the genes needed to express female phenotype aren’t even on the X chromosome, they are spread over the various autosomal chromosomes. To get a male, one need the genes on the Y chromosome, most particularly the SRY gene that first tells the proto-gonads to become a testes instead of the default ovary. But after that, nearly all the rest of sexual development is under the control of hormones produced by the testes.

If the body lacks the usual androgen (testosterone) receptor gene(s), even if that body has all the other typical genes and chromosomes for a male, that body develops in a rather typical female pattern. This condition is called 46XY CAIS, complete androgen insensitivity syndrome. They have typical testes in a seemingly typical female body phenotype, and most importantly for our discussion, women’s breasts at puberty.

Breast tissue does not care if there are XX vs. XY chromosomes. Breast tissue, like all secondary sexual characteristics that develop at puberty, are under the influence of sex hormones. Sex hormones can and should be viewed as specialized growth hormones. Various tissues express different sensitivities to the various sex hormones and will grow or not grow depending upon the presence and balance of these specialized growth hormones. In particular, breast tissue responds to estrogen and progesterone and are somewhat suppressed by androgens.

Circling back to transwomen, we note that Hormone Replacement Therapy (HRT) uses the very same hormones that induce breast tissue development in women. Transwomen have all the genes and breast tissue stem cells needed to develop fully functional FEMALE breast tissue. When a transwoman begins HRT, her breasts respond and begin to develop. After sufficient time, her breasts are histologically identical to adult natal female breasts. That includes the potential for lactation.

A woman does NOT have to have given birth or even have been pregnant to lactate. It certainly helps, given that certain hormones automatically are produced in amounts that prepare the breasts to produce first colostrum then milk, but isn’t an absolute requirement. The key requirement is that of tactile stimulation that a baby’s suckling produces and that once a flow of colostrum is present, that it be drawn out, either by a baby suckling or by manual expression / pump.

If a woman is adopting or working with a gestational surrogate, she may elect to breastfeed her baby by following a regimen of stimulation, expression, and pumping. In some cases, medication may aid in this process.

Many transwomen have produced colostrum due to HRT which in some cases, primes the breasts in the same manner as being pregnant. (I myself have produced colostrum.) If a transwoman is adopting, working with a gestational surrogate, or has a female partner who is expecting a baby, she too may elect to breastfeed her baby in the same manner as would any other non-birthing woman.

The milk produced by a transwoman is identical to milk produced by a natal female. Transwomen have been quietly, successfully, and safely breastfeeding babies for decades. They will continue to do so.

Biological Reality.

Further Reading:

Baby Hunger

References:

de Blok, et al, “Frequency and outcomes of benign breast biopsies in trans women: A nationwide cohort study” The Breast: Official Journal of the European Society of Mastology, (2021) https://doi.org/10.1016/j.breast.2021.03.007

Wambolt, R. et al, “Lactation Induction In A Transgender Woman Wanting To Breastfeed: Case Report”, Journal of Clinical Endocrinology & Metabolism, (2021), https://doi.org/10.1210/clinem/dgaa976

Kulski, J., et al, “Composition of breast fluid of a man with galactorrhea and hyperprolactinaemia”, Journal of Clinical Endocrinology & Metabolism, (1981), https://doi.org/10.1210/jcem-52-3-581

Breastfeeding Without Giving Birth

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