Transgender Breast Development: A lack of data is progress?

There is a trend in transgender research that I’ve noticed – a lack of evidence in either direction is often considered the “gold standard” for clinical practices. This is blatantly absurd.

1. Clinical Review: Breast Development in Trans Women Receiving Cross-Sex Hormones

Results: Only few studies with low quality of evidence addressed these topics. The available evidence suggests that breast development is insufficient for the majority of trans women and that type and dosage of hormonal therapy seem not to have an important role on final breast size.

Conclusions: Our knowledge concerning the natural history and effects of different cross-sex hormone therapies on breast development in trans women is extremely sparse and based on low quality of evidence. Current evidence does not provide evidence that progestogens enhance breast development in trans women. Neither do they prove the absence of such an effect. This prevents us from drawing any firm conclusion at this moment and demonstrates the need for further research to clarify these important clinical questions.

So cool. Thanks science! So you have confirmed we don’t really know anything about the effects of progestogens on breast development. Nicely done! Well doctors, it’s clearly time to throw progestogens out the window – who needs ’em! (seriously, who? we simply don’t know.)

2. Breast Development in Transwomen After 1 Year of Cross-Sex Hormone Therapy: Results of a Prospective Multicenter Study

The current study shows a modest increase in breast-chest difference after 1 year of CHT, mainly resulting in less than an AAA bra cup size. Age, weight change, smoking, BMI, serum estradiol levels, and estrogen administration route did not predict total breast development after 1 year of CHT.

An interesting finding is that main breast development occurred in the first 6 months of CHT. The flattening of the breast development curve in this study suggests no further increase in breast-chest difference after the first year of CHT. However, the maximum effect of CHT on breast development may be expected after 2 to 3 years, as also seen during pubertal development in girls (1, 5, 17). Because the follow-up of the current study is 2 year, no conclusions can be drawn on final breast development induced by CHT. Moreover, a recent study by Fisher et al. showed breast development to Tanner stage 3 after 2 years of CHT, which emphasize the need for studies with longer follow-up (18).

Wow! You mean after 1 year of HRT using 99% CPA as the AA and cookie cutter Estradiol targets, people responded poorly in terms of breast development? That sounds like progress to me! I guess the method of Estradiol and dosage doesn’t matter. Better continue the practice of non personalized medicine!

After the first 6 months of HRT breast development slows down? Well we should probably publish this study at 1 year when there is insufficient long term data so that doctors who don’t give a crap will take it seriously and not bother to personalize HRT approaches. Because science!

3. Relationship Between Serum Estradiol Concentrations and Clinical Outcomes in Transgender Individuals Undergoing Feminizing Hormone Therapy: A Narrative Review

The available evidence has not found that higher serum estradiol concentrations, together with suppressed testosterone, enhance breast development, or produce more feminine changes to body composition. However, ensuring testosterone suppression appears to be an important factor to maximize these physical changes. Higher serum estradiol concentrations have been associated with higher areal bone mineral density. Although the resultant long-term clinical implications are yet to be determined, this could be a consideration for individuals with low bone mass. The precise serum estradiol concentration that results in adequate feminization without increasing the risk of complications (thromboembolic disease, cholelithiasis) remains unknown. Further prospective trials are required.

Interesting that suppression of testosterone is important, and that happens largely based upon Estradiol levels; yet at the same time the data indicates Estradiol level has nothing to do with feminization outcomes. How can you decouple two things that are tightly coupled? Oh I see, we still don’t know and it needs further study – now the contradiction makes sense! Science++;

4. Effects of hormones and hormone therapy on breast tissue in transgender patients: a concise review

Conclusions: We conclude that the long-term effects of off-label pharmaceutical use for modulation of hormone levels and sexual characteristics in transgender patients have not been well studied. The tendency of steroid hormones to promote the growth of certain cancers also raises questions about the safety of differing doses and drug combinations. Further clinical and laboratory study is needed to better establish safety and dosing guidelines in transgender patients.

Uhh… do I really need to explain that? Science??

5. Dr. Powers theories on Transfeminine Breast Development

I freakin’ love this critique of Dr. Powers ideas in his v6 presentation:

I just want to point out that Dr. Powers is a GP who is a hobby scientist trying to help Transgender patients who have had bad experiences with other doctors or poor outcomes from cookie cutter approaches. He is just trying to solve problems for people and sharing his limited data and outcomes. Obviously he is largely using basic research and intuition along with clinical observations.

The part that makes him great is that he publishes his findings and gets constantly slammed for it. It takes a lot of courage to open yourself up to peer review. How many doctors would be highly criticized for practices / misconceptions / etc. if they were published as openly? I’d bet most of them who were legitimately trying to help patients with specific problems.

So if Dr. Powers sees a clinical outcome and it’s a single case/situation, the most he can do is talk about it openly and raise questions. The problem is that people want simple answers to complex problems. Doctors want limited liability and a basic handbook for HRT practices – that results in conservative standardized medicine with limited outcomes for patients.


At the end of the day if someone with limited feminization tries something novel and it works, then it works. Who cares about the statistical significance to the rest of the population who are not in the same genetic situation? Are you going to throw out a good result because it doesn’t apply to everyone?

There are populations with very specific genetic situations such as rare diseases – should we ignore them? Guess what? We already do ignore them. There are many Facebook groups dedicated to these limited populations and the handful of family/friends who care about these people who often suffer greatly from a lack of popular interest.

I will take a survey of findings on social media over some of these “scientific” studies that have no conclusions any day.

These broad statistical studies are taking limited clinical data and crunching the numbers as best they can in an attempt to prove a point. To get published you need to prove a point – since there is nothing to say due to limited data they spin the publication as “there is no data to support X”… cool, because they directly state that more information is needed to reach a conclusion. The problem is that people (including doctors) interpret these publications as evidence when in fact they are publishing a lack of evidence based upon a lack of data.

Further Reading

I’ve written quite a few articles with overlap on some of these topics, included below for further reading.

Leave a Reply

Your email address will not be published. Required fields are marked *