Breast Development
(In Male-to-Female Transsexuals)

For all women, breasts are a very important and very visible aspect of their "womanhood", it is also probably fair to say that the female breast is regarded as a key aspect of feminine beauty, both in our modern society and historically - and with both men and women.

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 woman will have breast implants, the first step is always female hormone treatment, using oestrogen and anti-androgens to enable the growth of breasts to their maximum natural size - although this is somewhat less than that of close female relatives.  Breast growth can often be enhanced by use of an appropriate progestrogen, causing a more natural breast shape to form with lactative and ducting tissue as well as the fatty tissue laid down by oestrogen treatment.  If the woman starts treatment already past puberty, the resulting breast development can range from respectable to very disappointing - although even in the later case it should be noted that modern bra's, "push-ups" and breast enhancers can still do wonders appearance wise.  But the final breast development may still be regarded as unsatisfactory, particularly in older patients, in which case implants may be desired.

The Breast
A breast (also known as a mammary gland) is a quite complex structure consisting of a mass of fatty tissue and nerves served by a good blood supply.  Fully developed, each breast when lactating is capable of supplying a pint or more a day of nourishment (milk) and immunoglobulins to a nursing infant.  Visible in the centre of the breast is the protruding nipple, which is surrounded by a pigmented circular area called the areola.  Small glands in and around the nipple provide lubrication and protection against infection, which is particularly important for breast-feeding mothers.  Produced by the lobules (consisting of alveoli) in the interior of the breast, milk is carried to the nipple by a collection of tubes known as ducts. 

 Stages of Mammary (Breast) Development
At birth the rudiments of the functional mammary gland are in place: the nipple and areola are formed along with a rudimentary system of mammary ducts extending into a small fat pad on the chest wall.   The mammary gland remains a rudimentary system of small ducts until puberty when the advent of oestrogen secretion by the ovaries brings about the first stage of the four stages of mammary development: mammogenesis, lactogenesis, lactation and involution.

Mammogenesis commences at puberty with the onset of oestrogen secretion by the ovaries, usually between the ages of 10 and 12 in the genetic girl.  Oestrogen causes 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.  About 40% of male children also initiate mammary development during puberty due to the tendency of the testis to secrete significant quantities of estrogens in early phases of its development.  As testosterone secretion increases this function is lost.

Oestrogen stimulates breast growth by acting on the mammary tissue.   With the onset of the menstrual cycle 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 course 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.

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.

Lactogenesis (referred to as the time when the milk "comes in") starts about 40 hours after birth of the infant and is largely complete within five days. 

When nursing has ceased the gland undergoes partial involution, losing many of its milk producing cells and structures, a process that is only completed after menopause. 

Breast Development in the Transsexual Woman
Every person whether genetically male or female is born with milk ducts — a network of canals that transport milk through the breasts — present from birth.  In the male-to-female transsexual woman the mammary glands stay quiet until commencing female hormone treatment releases a flood of oestrogen's, causing them to grow and swell in what is effectively a female puberty and initiating the first phase of mammogenesis. 

Externally, breast growth and development is medically defined by "Tanner's Five Stages":

Tanner Stage	Description (as applies to transsexual woman)	Example
Stage I (Pre-hormone treatment)	The undeveloped "pre-adolescent" pre-hormone type breast consists of a small elevated nipple (papilla) only, with no significant underlying breast tissue.
Stage II (Hormone treatment started)	After 6-8 weeks of hormone treatment subareolar nodules can be (painfully) felt and the nipple becomes very sensitive.  After about three months breast buds will visibly start to form. There is an elevation of the breast and nipple as a small mound and the areola diameter may begin to enlarge (particularly in young women).  Milk ducts inside the breast begin to grow.
Stage III	This stage is reached after between six months and a year of continuous treatment. There is further enlargement and elevation of the breast and areola (with no separation of their contours).  The areola may begin to darken in colour.  The milk ducts give rise to milk glands that also begin to grow.
Stage IV	It will take one to two years to reach this stage.  There is projection of the areola and papilla to form a secondary "mound on a mound" above level of breast.
Stage V	Only a very few transsexual women (usually under age 20) reach this "mature" stage, after perhaps two years hormone treatment. The breast has now fully filled out and only the nipple still projects, the areola has recessed and become part of the general breast contour i.e. the secondary mound has disappeared.

After female hormones are commenced the breast slowly evolves and gradually increases in size, often with periods of growth and periods of apparent standstill.  In the initial phase of oestrogen hormone therapy subareolar nodules, which can be painful, are common.  

Both oestrogen and progesterone should be taken, it's thought that oestrogen stimulates cell mitosis and growth of the ductal system, while growth, development and differentiation of the glandular tissue (called lobules or alveoli) seems to be dependent on progesterone, and breast fat accretion seems to require both.  

Sarah, a 24 year-old transgirl after 10, 17 and 26 months on hormones.

It may take two years to achieve full growth so patience is essential.  Dissatisfied girls rushing to seek breast implants after one year may then experienced complications and misshaped breasts when another spurt of breast tissue growth sets in.  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 calm and well-lit study is made of them.

This 53 year-old transwoman has been on hormones (0.675 mg Premarin, 10 mg Progesterone, 2 mg  Estrofem) for 7 years.

The final amount of breast development obtained by a transsexual woman on hormone treatment is quite variable, but it known to be very age dependent - unfortunately the younger the person is and the more recent puberty (which normally ends between 18 and 20), the better the development will be.  Genetics also plays 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! 

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 diminishes as they are swallowed by the surrounding "padding".    

The limited evidence would indicate that maximum results are obtained by starting female hormone treatment just before the on-set of male puberty, but when puberty ends (around age 18) a "switch" in the body seems to turn off and the likely amount of breast development rapidly falls away.  Thus a 12 year-old boy-to-girl will typically end up with well developed breasts not that much smaller to his sisters and mother, and the same person starting hormone therapy as a 20 year-old will often still have quite good results, but as a 30 year-old he/she will have much less satisfactory results, and will be only slightly better off than a 40 year-old who in turn will be almost no better off than a 50 or more year-old. 

Anecdotal evidence (clearly there is a need for medical studies) indicates that the best possible natural bust development achievable by transwomen, normally young transwomen, is about one bra cup size less than that average for close female relatives.  

After augmentation via the inframammary method, Caroline Cossey became a 36C bra size and displayed a fairly natural bust appearance in her famous Playboy spreads.

It must be emphasised that although most girls who are able to start hormone treatment while in their teens will eventually develop full Tanner IV or V, "B" or even "C cup" breasts, 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.  Conversely, while most of those women starting hormones when already in their mature years will achieve only slight Tanner II or III "AA cup" breast buds, a few will get adequate, even ample, breast development.

Realistically, most adult 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".

Also many transsexual women, particularly those starting hormones over about the age of 25, suffer from under-developed or hypoplastic breasts.  Such breasts are very small or narrow, lack normal fullness, and may seem bulbous or swollen at the tip due to an over-prominent nipple-aereolar complex - their narrow elongated appearance leads them to be termed "tubular breasts", and nicknamed "snoopy breasts".  The shape is caused by a failure to sufficiently develop the glands and lobules which help fill out the breast.  As a tubular breast consists primarily of just fatty tissue, milk production and breast feeding can be problematic - although of course this is very 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 can make it difficult to monitor the degree of breast development using the Tanner scale in mature transsexual women.

Breast Size
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, in 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.  Consequently, 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).

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 women object to this too much!   

Examples
The following ladies are all believed to be transsexual women with natural breasts developed from hormone use only.  I have attempted to classify using the Tanner stage, this system can be hard to apply to the breasts of transsexual women and my grading can be debated in several cases.  Notice the relatively small areali, even with the greater breast development.

Please contact me if you know that any are not transsexuals, or if they have had breast augmentation.

Early Tanner II budding	Tanner II	Tanner III - typical final type breast development when starting hormones in 40's
Tanner III, started hormones age 25, after 18 months use	Tanner IV, probably started hormones as young teenager	Tanner IV, started hormones age 23 (with 200ml implants)
Tanner V	Small Tanner V, started hormones about age 19	Good size Tanner V,  started hormones age 13

And a few more examples kindly sent to me by women of their breast development:

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