Hair and body hair are among the features that change most during medical transition, and until now the evidence has rested almost entirely on what people reported about themselves. A team at the Center of Expertise on Gender Dysphoria at Amsterdam UMC (Netherlands) has gone a step further: it measured terminal hair — the thick, pigmented kind — with digital microscopy in a 12-month longitudinal follow-up of 36 transgender people starting gender-affirming hormone therapy. The results are published in The Journal of Clinical Endocrinology & Metabolism.
What was measured and how
Twenty transgender men and 16 transgender women took part. At each visit — before starting hormones, at 3 months and at 12 months — several areas were photographed with digital microscopy: upper lip, chin, upper and lower abdomen, and thighs. Hair density was counted per square centimetre, with no reliance on subjective scales. The team also assessed psychosocial impact using the Body Appreciation Scale-2 and satisfaction questionnaires.
What the numbers show
After 12 months, transgender women — receiving estrogens and antiandrogens — showed significant reductions on the upper lip (−17 hairs/cm²; CI −32 to −2), chin (−28 hairs/cm²; CI −47 to −8) and upper abdomen (−6 hairs/cm²; CI −12 to 0). One striking detail: there were no relevant differences between those who had undergone laser hair removal and those who had not, suggesting that the portion of the effect attributable to hormones themselves is measurable on its own.
Transgender men on testosterone showed the opposite and broader pattern: increased density on the upper lip (+21 hairs/cm²; CI 11-30), chin (+13; CI 3-24), upper abdomen (+17; CI 8-23), lower abdomen (+20; CI 11-28) and thighs (+14; CI 7-21).
Beyond the mirror: body and identity
The work did not stop at counting follicles. Both groups improved their body appreciation, their satisfaction with hair growth and their sense of gender congruence over the 12 months. In other words, measurable physical changes moved alongside a better relationship with one’s own body — a finding consistent with what clinical literature describes about wellbeing during gender-affirming hormone therapy.
The authors themselves flag the limitations: the sample is small (36 people) and comes from a single centre, so the findings should not be generalised as rules or used to set individual expectations. Even so, they highlight that digital microscopy is emerging as an objective, inexpensive tool for comparing different hormone regimens in future work — useful when clinical teams need to adjust doses and manage expectations.
Why it matters
For many people on hormone therapy, facial and body hair is not an aesthetic detail: it is part of how they recognise themselves in the mirror and on the street. Having objective measures of how much changes, where and over what time frame makes it possible to inform patients better before starting treatment, to set realistic expectations and to avoid both exaggerated promises and hard-to-swallow disappointments. It also opens the door to studying why some people respond more than others.
The study does not address the biological basis of gender identity — it measures an effect of treatment, not a cause — but it adds solid clinical data on how the body responds to gender-affirming hormones and how that response intertwines with self-perception.
Source: Quantitative effects of sex hormones on hair growth and patient satisfaction. de Kroon RWPM, Strating J, Heijboer AC, den Heijer M. The Journal of Clinical Endocrinology & Metabolism 2026;111(9):2426-2435. DOI: 10.1210/clinem/dgag139.
Article published on dosier.es. Image generated with artificial intelligence (marta ai → marta.syf.es).
