Endocrine Abstracts

Background: In male to female transgender patients breast development is a key part in the process of feminization using cross sex hormone therapy. In the Endocrine Society’s clinical guideline ‘Endocrine treatment of transsexual persons’ the onset of breast growth is estimated as 3–6 months after starting cross sex hormone treatment. The maximum breast growth however is seen after 2–3 years. But how much growth, in centimeters or cup-sizes, we can expect is not clear. With this in mind we want to objectify the breast growth after one year of cross sex hormone treatment in male to female transgender patients.

Objective: To examine the absolute increase in breast circumference corrected for chest circumference in male to female transgender subjects included in the ENIGI database who are treated with cross sex hormone therapy for 1 year.

Methods: All male to female transgender subjects included in the ENIGI database who have been treated with cross sex hormones for 1 year are eligible for this study. According to the ENIGI protocol patients are examined in the outpatient clinic every 3 months. During this outpatient clinic visits several features are examined and measured including breast and chest circumference. Missing values we imputed with multiple imputation(ICE) in Stata.

Results: One-hundred-forty-two male to female subjects are eligible for this study. Mean breast circumference increased from 93.9 (S.D. 11.6) cm to 97.2 (11.1), while chest circumference remained stable (88.6 (10.7) cm). The mean difference between breast and chest diameter after one year was 7.5 (3.0) cm. This implicated a C-cup (16–18 cm) in 2%, B-cup (14–16) in 4%, A-cup (12–14) in 8% and AA-cup (10–12) in 10% of the patients. After 1 year, 76% had a breast-chest difference smaller than 10 cm.

Conclusions: Our study shows a modest breast development after 1 year. Future studies need to determine whether breast circumference is an accurate method to estimate breast development during cross sex hormone treatment and what the effects are on longer treatment. Furthermore, a topic of interest is which factors influence breast development in transgender treatment.