I read the entire study. For one, yes, it's too soon to conclude anything. It takes several years before breasts reach their final size and even then, they will continue to change for an entire lifetime in accordance with several factors (diet, stress, age).
Segundo...estradiol levels were quite low. Mean estradiol levels in the 4th quartile, where those were the highest, were 567 pmol/L (154 pg/ml) and lowest were 110 pmol/L in the first quartile (29 pg/ml). Is it any surprise that breast development was poor? Except for oral estradiol, the doses prescribed were typical of those prescribed to menopausal women to stave off vasomotor symptoms and maintain bone density but perhaps (IMO, most certainly) too low to trigger development of female secondary sexual characteristics (i.e. breast growth).
Given our context and history, it may be perfectly plausible that, at least some of us need higher levels and doses to achieve the same degree of breast development (or even greater, to fill out our chests) as ciswomen. For the most part, we have much lower growth hormone levels at the moment of development, are older (different telomere length), and were exposed to a very different hormonal environment in-utero which may possibly (based on studies in rats/mice) make us less sensitive to estrogen.
Horm Metab Res. 1994 Sep;26(9):428-31.
"Estradiol increased from 34.8 +/- 7.5 pg/ml to 3226 +/- 393 pg/ml after 3 months and to 2552 +/- 254 pg/ml after 6 months, respectively, in group A." (six patients, 49.5 +/- 4.8 yrs old)
"In group B estradiol increased from 27.8 +/- 6.5 pg/ml to 3028 +/- 728 after 3 and to 2491 +/- 684 pg/ml after 6 months."
"The treatment was well tolerated. No adverse effects were seen, the patients expressed a feeling of particular well being, 3 of them wanted to have the injections repeated and none of them wanted to stop treatment because of troubles or side effects."
"Pseudopregnancy had been used in sterile patients with hypoplasia of the uterus and for hypoplasia of the breasts (Kaiser 1959; Lauritzen 1992)."
"We have experience with therapeutic pseudopregnancy in about 200 patients with mammahypoplasia (Lauritzen 1992). Its rate of objective and subjective tolerance is excellent."
"Investigations of lipids, liver enzymes and haemostasiology to be published later will show the absence of unwanted metabolic effects of this regimen."
"The increase of bone density in our patients with gonadal dysgenesis was associated with an impressive secondary sexual development, especially of the breasts."
"In conclusion, our data show, that the treatment (...) by means of high parenteral estrogen-progestogen depot injections is effective. Virtually no side effects occurred. The therapy is well accepted by the patients."
"In addition, pseudopregnancy may be useful and effective in osteopenia and lacking secondary sexual development due to gonadal dysgenesis like in Ullrich-Turner syndrome (after completion of growth), where substitution doses of ovarian hormones may be not sufficient enough to guarantee satisfactory response."
