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Hormone therapy
In gender treatments, cross-sex hormones are administered to push the body in the direction of the other sex. This is not a top-up for a deficiency, as in endocrine conditions, but a pharmacological switch of a healthy hormonal system. The consequences are far-reaching, partly irreversible, and lifelong medication is required in virtually all cases.
Feminising hormone therapy
Trans women and some non-binary people receive oestrogen, usually combined with an anti-androgen (cyproterone acetate, bicalutamide or spironolactone) to suppress testosterone. Effects include breast formation, fat redistribution, reduction of muscle mass, decreased erectile function and sperm production. Voice and skeleton no longer change; body height, shoulder width and hands remain male.
Breast formation and sperm-cell damage may be permanent. After removal of the testes (orchidectomy), lifelong oestrogen substitution is required to counter bone loss and other consequences of a hormone-deprived state.
Masculinising hormone therapy
Trans men receive testosterone by injection, gel or patch. The voice deepens, facial and body hair increases, the clitoris enlarges, menstruation usually stops, fat distribution shifts and muscle mass increases. Voice deepening, hair growth and clitoral enlargement are permanent. Breast tissue does not disappear with testosterone; for that a mastectomy is required.
With long-term use, the body's own sex-hormone production may decrease or stop. After removal of the ovaries, lifelong testosterone substitution is needed.
Indication and access
In the Netherlands, hormone therapy in adults starts after a diagnostic process in a specialised centre (Amsterdam UMC, Radboudumc). Due to enormous waiting times and the expansion via GP-led care and foreign providers, the diagnostic preliminary process is sometimes limited in practice. Self-medication via the internet occurs and is medically risky. See waiting times and care pathway.
Effectiveness: what we know, and what we do not
Studies of psychological well-being after hormone therapy often show positive results at the group level, but the methodological quality is weak across the board: small groups, short follow-up, high attrition, no control group, and outcome measures that lean strongly on self-report by a motivated group.
The Cass Review (2024) rated virtually all evidence for hormone therapy in young people as 'low' or 'very low quality'. The Swedish SBU and the Finnish COHERE drew comparable conclusions. For adults the evidence is somewhat firmer, but long-term studies (>10–20 years) are scarce. That is medically unusual for a treatment that is in practice continued for life.
Risks
Oestrogen increases the risk of thrombosis (particularly orally), affects the cardiovascular risk profile, can burden liver function and, with long-term use, is potentially linked to breast cancer. Cyproterone acetate is associated with meningioma. Testosterone causes erythrocytosis (raises thrombosis risk), can adversely affect the cholesterol profile and produces vaginal atrophy. For both hormones, lifelong dosing and lifelong monitoring apply. See side effects of hormone therapy.
International policy shift
Since 2020, Sweden, Finland, Norway, Denmark and the UK have tightened access to hormones for minors or restricted it to research settings. They base themselves on systematic evidence reviews concluding that the benefits in young people are insufficiently demonstrated to justify the risks. The Netherlands has not yet published a comparable evaluation.