|Note: I wrote the first version of this page in 1999. At that time, I could find no medical studies describing breast development in male-to-female transsexuals, but the burgeoning World Wide Web included numerous accounts by transwoman (particularly on the GeoCities hosting site) reporting good "B-cup" breast development after just six-months on hormones, and "D-cup" after a year or two. I took these reports with what I thought was large pinch of salt, but - based on subsequent reading, conversations, and personal experience - this page was initially far too positive. I have since made edits to reduce expectations but the article is now very dated. However I believe that it remains an interesting read, if treated with caution.|
For all women, breasts are a very important and very visible aspect of their "womanhood". The display or even the indication of breasts is instinctively viewed by observers as a strong evidence that someone is female. Breasts are regarded by both men and women as a key aspect of feminine beauty - in our modern society and historically.
The development of breasts gives the male-to-female transsexual woman a tremendous confidence boost, and powerfully identifies her as a female to others. It is also impossible to ignore that the fact that breasts are immensely strong sexual symbols, and secondary sexual organs whose presence can be enjoyed by both the owner and their partner. Unlike a vagina, breasts can be easily and acceptably be publicly displayed in either part (cleavage) or full (e.g. topless sun bathing), or prominently implied underneath a skimpy top. Bra's and [usually] breast forms/padding are essential early purchases for every transsexual woman.
While ultimately many transsexual women will have breast implants, the first step is always female hormone treatment to enable the growth of breasts to their maximum natural size - although this is usually somewhat less than that of close female relatives. If the woman starts treatment already past puberty, the resulting breast development can range from respectable to very disappointing - although even in the latter case it should be noted that modern bra's, "push-ups" and breast enhancers can still do wonders appearance wise.
Above, the male breast, and below the female breast
Development in the Genetic Woman
Mammogenesis commences at puberty with the onset of oestrogen secretion by the ovaries - usually between the ages of 10 and 12 in a genetic girl. Oestrogen (often spelt 'Estrogen' in American English) stimulates breast growth by acting causing enlargement of the mammary fat pad, one of the most oestrogen-sensitive tissues in the human body, as well as lengthening and branching of the mammary ducts. The development occurs according to well-defined milestones called Tanner stages:
The levels of oestrogen required to cause breast development are surprisingly low - until stage IV, the growth of the breast in a girl takes place with oestrogen levels similar to an adult male. That is why about 40% of male children also initiate "Tanner I" type mammary development during their puberty due to the tendency of their testis to secrete significant quantities of oestrogens in early phases of its development. However, as testosterone secretion increases the breast development ceases and very few boys reach the Tanner II stage.
It takes just two to three years for a girl to achieve the majority of her breast growth. Stage V is aligned with the onset of the menstrual cycle - which results in the production of progesterone for the first time. The presence of progesterone stimulates the partial development of mammary alveoli, so that by the age of 20 the mammary gland in the woman who has not been pregnant consists of a fat pad through which pass 10 to 15 long branching ducts, terminating in grape-like bunches of mammary alveoli. In the absence of pregnancy, the gland maintains this structure until menopause. It's worth noting that these ducts are very small and contribute little to breast size - this is one reason why some doctors consider the prescription of progesterone to be unnecessary for transwomen.
In Europe and the USA more than half of adult genetic women (post-puberty, pre-menopause) are naturally a B or C bra cup, relatively few (<25%) women are a D cup or greater. But the figures vary widely from study to study, e.g. Triumph's European Bra Size Survey from 2007 famously found that 57% of UK women were a D cup or more (18% C, 19% B, 6% A), and the average size increased to DD in the 2015 survey! These highly improbable findings are undoubtedly biased by the absence of any checking of the submitted responses.
Mammogenesis is completed during pregnancy, with the gland becoming able to secrete milk sometime after mid-pregnancy. Pregnancy is often considered to be the period of most extensive mammary growth. Indeed, extensive lobular and alveolar development occurs only during pregnancy. During pregnancy, it is not unusual for a woman's breast size to temporarily increase by a full cup size.
Lactogenesis (referred to as the time when the milk "comes in") starts about 40 hours after birth of a baby and is largely complete within five days. When nursing ceased the breast undergoes partial involution, losing most of its milk producing cells and structures. Many women have slightly smaller breasts after pregnancy and nursing because they have less fatty tissue and once the breast is no longer swollen with milk it can sag in an unsightly manner.
Innovolution completes after menopause, when most women move to a smaller bra size. However since the 1990's hormone replacement therapy has become a very common treatment for women starting their menopause, this can actually stimulate breast development and it is not unusual for bra size to actually increase.
Development in the Transsexual Woman
In the initial phase of hormone therapy subareolar nodules - which can be painful - are common. Both oestrogen and progesterone (despite the reservations of some professionals) should be taken - oestrogen stimulates cell mitosis and growth of the ductal system, whilst the growth, development and differentiation of the glandular tissue (lobules or alveoli) seems to be dependent on progesterone, and breast fat accretion seems to require both. A transwomen with well-developed breasts is thus quite able to nurse - given the right stimuli.
It's important to realise that the results of female hormone treatment eventually become obvious to everyone, whether called breasts or "man boobs". For the pre-transition woman on hormones - it becomes increasingly difficult and embarrassing to go topless - local swimming pool, the beach, or in the bedroom with a partner.It takes about two years of hormone therapy for a transwoman to achieve maximum breast growth. Unfortunately, even if this quite generous, the overall appearance of the breasts is often hampered by the girl having a larger than average (for a woman) chest cage.
Because the bony frame of the male chest differs greatly from the female, the resulting appearance of the thorax still differs from that of similarly developed natal females, often resulting in an appearance that is deemed unsatisfactory by patients, leading approximately 60% to request an augmentation mammoplasty.
Although often only partially developed, the breast structure of a transsexual "XY" woman is basically the same as a genetically "XX" woman after the first phase of mammogenesis. Thus medical information and rules about female breasts (including the need for regular breast self-examination and mammogram's) apply just as much to transsexual women taking oestrogen as they do to genetic cis-women.
All transsexual women like to 'round up' the breast development they achieve from hormones and other more uncertain methods. But multiple studies paint a rather depressing picture.
Breast size can be quantified by measuring the maximum hemi-circumference over the nipple with a flexible tape. The following table shows the results from one study of breast development, measured in the sitting position, of 500 transsexual women:
It clearly shows that the breasts of male-to-female transsexual women are considerably smaller than genetic XX women. To make matters worse, the width of the average transsexual woman's thorax is greater than that of the average female thorax, and so the breast development is proportional to the chest size even less than the figures indicate.
A second study published in 2017 of the breast development of 229 transwoman after one year on hormones (estrogen and antiandrogen) showed similar disappointing results. This used the approach of measuring the circumference of the chest underneath the breasts and at the largest part of the breasts. The difference between these two measurements was then used to determine breast growth and bra size.
To compound the disappointment, the study showed that almost all of the breast growth happened during the first six months of treatment, and that it had tapered to almost no growth by the final three final three months. I.e. it seems that a transwoman has not achieved substantial breast growth after six months on hormones, she is unlikely to be much better off several years later.
The final amount of breast development obtained by a transsexual woman on hormone treatment is undoubtedly very variable and depends on a numbers of factors:
Firstly, and one thing no MTF transwoman can do anything about, is the fact that their body has since the foetus stage been exposed to larger amounts of testosterone hormones than a girl. The cumulative effect on the body is very significant - the most obvious early differentiation is a penis rather than a vagina, but there does seem to be a significant impact on potential breast growth as well. Women suffering from AIS (i.e. genetically XY male, but unaffected by androgens) are as well endowed bust wise as their female relatives, so the constant drizzle of testosterone in the womb and onwards seems to have an irreversible effect on the potential breast development of "boys".
Secondly, genetics also play a very significant role - some people are genetically predisposed to have copious amounts of fat cells in therefore large breasts, others practically none. Thus amply endowed sisters are a promising sign that development will be good, while flat chest'ed sisters are a serious worry!
Thirdly, breast growth seems to be very age dependent - the younger a person and the more recent puberty the better the development will be. Since about 2001 it has become quite common for young transgirls to be prescribed puberty blockers. These have very important effects such as preventing facial hair and the voice deepening, but they don't seem to stop the clock on potential breast development.
The limited available evidence indicates that for the best possible breast development, oestrogen hormone treatment (rather than just puberty blockers) should begin before the on-set of male puberty. It appears that transgirls who start taking oestrogen hormones around age 12/13 are likely to achieve reasonable natural breast growth after a few years, but conversely these girls are rare. Most instances in Europe involve unsupervised medication. In terms of breast volume, the final result is then likely to be only slightly less than the girls mother and sisters. However such hormone treatment is unsupervised and the results are unverified as the Standards of Care prevents (for many good reasons) the hormone treatment of adolescents under age 16.
Age Matters - A Lot ...
Towards the end of puberty (age 15 to 17) a "switch" in the body seems to turn off and the likely amount of breast development rapidly falls away to a much lower level. Thus a 12 year old boy-to-girl might develop breasts not much smaller to his sisters and mother; the same person starting hormone therapy as a 18 year-old might still have reasonable results; but as a 30 year-old she will have far less satisfactory results, and this will be only slightly better than a 40 year-old who in turn will be barely better off than a 50 plus year-old.
Other smaller factors come into play in determining the size of a woman's breasts, including nutrition, exercise, health, and weight. For example, if a woman's body weight falls below its optimum then her breasts can shrink dramatically as the fat cells in them are burnt up (or in the case of a skinny transwoman are perhaps never deposited), while if her weight is above optimum then the apparent or relative size of her breasts may diminish as they are swallowed by the surrounding "padding".
Currently (2015) the very earliest age at which a transgirl is likely to be prescribed hormone treatment by a doctor is 16, with 18 more probable. Whilst most girls who start hormone treatment in their teens seem to eventually develop "B cup" Tanner IV or V type breasts, even this is still by no means certain. For example the model Caroline Cossey started hormones at age 17 but owes most of her famous 36C chest to implants two years later, and Caroline is far from unique.
It appears that 18 is already beyond the optimal age for good breast development. Certainly many young transsexuals are dissatisfied with their breast growth as they compare themselves with other girls, and begin to compete for boyfriends.
Conversely, while most transgender women starting hormones when already adult will achieve only slight Tanner II or III "AA cup" breast buds, a few will get adequate, even ample, breast development.
There is undoubtedly often a degree of wishful thinking and 'rounding up' in the bra sizes claimed by transsexual women. The claims often made by middle aged transwomen to have developed C or D cup breasts after a year on hormones should be treated very sceptically.
Realistically, most transsexual women starting hormone treatment over the age of 20 will be very lucky if they eventually genuinely fill a "B cup" bra from hormone use alone, and those over 30 an "A cup". However, if letters are important it should be remembered that despite a perception created by television and the press, the average cup size of genetic women is actually only "B".
An unscientific poll in 2001 of seven transgirls who began taking estrogen in their teens showed that they all reached a good A apple or reasonable B cup, i.e. only slightly smaller than genetic women. Even more interestingly, none had had breast augmentation - they were generally happy with what nature had endowed them with, after a little prompting! This finding differed significantly from older transwomen, and seemed to strongly support the view that a transwoman's age matters a lot where breast development is concerned.
Fast forward to 2015, and I have become increasingly puzzled by the complaints of young transgirls that after several years on hormones, they still have little or no breast development. On reflection, I think several factors apply:
The end result of the current approach often seems to be a 21-year old transwoman who despite (or rather, because of) years of medical treatment still looks like a young teenage boy physically, whilst in the same time her younger sister has transformed into a buxom woman.
I suspect that the medical profession needs to become far more aggressive in the prescription of female hormones for transgender children in the 14-17 age group (accepting the risk of the occasional mistake), and that pressure for this will start building.
The Areola of Transwomen
One odd problem that transsexual women face is that their areola - the coloured skin surrounding the nipple - rarely expands in accordance with 'normal' female breast growth. The areolae of a man averages about 25 mm (1 inch) in diameter, but few woman are under 30 mm and 50 mm is common, and the areola of women who have large breasts or who are lactating may be over 100 mm (4 inch) in diameter. Unfortunately even well-endowed transsexual women tend to have male type arealoe - this seems to be a genetic limitation as AIS women (who are also genetically XY) face a similar problem despite otherwise above average breast development.
Another characteristic of the breasts of MTF transsexual women compared with genetic women is the smaller average diameter of their areola, even if the breasts themselves are actually quite generous in size. Only starting hormone treatment at a young age seems to avoid this tendency. Also, because the breasts of transsexual woman rarely reach full Tanner V size and maturity, their nipples often appear very prominent - although few object to this.
As a tubular breast consists primarily of just fatty tissue, milk production and breast feeding can be problematic - although of course this is rarely relevant for transsexual women. The use of a "cocktail" of hormones that includes both oestrogen and progesterone may help reduce hypoplasticy.
In older transwomen, their small breasts are also likely to be spaced widely, and one breast is often noticeably larger than the other. These problems make it difficult to monitor the degree of breast development in mature transsexual women using the Tanner scale.
The overall effect and appearance of their hormone-only induced breasts is judged unsatisfactory by some 50-60% of MTF transsexual women, and the vast majority of these seek augmentation mammaplasty (breast implants).
Dissatisfied girls rushing to seek breast implants after just one or two years on hormones may then experience complications and misshaped breasts when another spurt of breast tissue growth sets in - as is quite common after SRS or an orchiectomy. It should also be expected that the breasts will grow unevenly, e.g. the right may become much fuller that the left. In the long-term the differences will mostly even out, but even in mature genetic women there is often a quite visible difference in size and shape between the left and right breasts when a study is made of them.
The advent of the first, very expensive, female hormone treatments in the 1950's was a massive advance for transsexual women seeking 'natural' breasts. Since then there have been improvements in potency, delivery and cost - but no fundamental progress in the likely final result. Breast augment surgery has been the reluctant last resort of many transwomen.
The last decade has seen the emergence of a solution for transwomen who want to increase the size of their hormone induced breasts without surgery. This essentially involves injecting fat cells into the breast tissue. Fat is taken through liposuction from the woman's belly or bottom. The fat cells are filtered out from the extract and then put into a cartridge for injection into the breasts maybe an hour later under local anaesthetic. About 30% of the immediate gain is quickly lost, but for many transsexuals this technique represents an alternative to breast augmentation, and it is claimed that an increase of two cup sizes (e.g. a B-cup to a D-cup) is possible.
The transfer process is being refined by prioritising the injection of stem rather than fat cells.
Assuming that hormones is the right route, patience is essential, it will take at least two years to achieve full breast growth and some imperceptible changes will continue for the rest of your life - as trying on a very old bra will reveal.
The earlier in life that oestrogen begins the better, but some girls who began treatment as young as 16 still have have only Tanner II/III type budding years later.
The accumulated evidence indicates that the average transwomen will eventually achieve a breast circumference and volume of breast tissue slightly less than the average for natal cis-women. About 30% transwomen genuinely achieve at least a B-cup, compared to at least 50% of natal women in Western Europe. Because the large skeletal frame of most transwomen, even good hormone induced breast development appears visually inadequate. One study of 60 transwomen incidentally mentions that 58 had had breast augmentation, with a high degree if satisfaction with the results.
A Final Warning
Taking hormones hoping to somehow become a closet page 3 girl - but without anyone at work or even the wife noticing - is simply unrealistic. Breast growth is irreversible without reduction surgery, stop taking the hormones and the breast growth that has been stimulated will still be around ten years later, it does not melt away.
Further - breast tissue means the risk of breast cancer. In the UK this is the direct cause of death for 15% of women, whilst it's negligible for men. Transwomen are less susceptible than natal women to breast cancer - probably because of the late and limited nature of the average transwoman's breast development - but it's now a significant risk. Signs of breast cancer include a lump in the breast, a change in breast shape, dimpling of the skin, fluid coming from the nipple, a newly inverted nipple, or a red or scaly patch of skin. Transwomen over 50 who have been on hormones for ten years or more should seriously consider regular mammography screening.
Please contact me if you have any comments.
Below are pictures sent to me by transgender women of their hormone induced breast development (i.e. with no implants). They confirm that breast development in XY transwomen is much less than that in most natal XX women.
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Copyright (c) 2015, Annie Richards