Debate › Precautionary principle · Last reviewed 2026-05-17

The endocrinological double standard

Analysis of the inconsistency between the precautionary regime that has governed mainstream endocrinology since the Women's Health Initiative (2002) and its absence in cross-sex hormone therapy. See also Cass Review 2024 and Karolinska 2021.

1. The paradox in one clinical question

Pose this question to an endocrinologist: why is testosterone prescribed with such caution to a 55-year-old man with laboratory-confirmed hypogonadism, while the same testosterone is delivered without comparable hesitation to an endocrinologically healthy 18-year-old woman seeking to masculinise her body? The question is rarely asked aloud — but it reveals the entire field of gender medicine as an exception to the endocrinological standard.

2. Mainstream caution since WHI 2002

For same-sex hormone replacement, the rules are clear: only on documented deficiency (hypogonadism, severe menopausal symptoms), lowest effective dose, shortest necessary duration, periodic monitoring of blood values, prostate, mammary tissue and liver function, and continuous weighing of thrombotic, cerebrovascular, oncological and cardiovascular risks. The Women's Health Initiative trial¹ triggered a fundamental recalibration: hormone replacement in women caused more breast cancer and cardiovascular events than previously assumed. The directive has been unchanged since: prescribe sparingly, on clear indication, with regular evaluation.

3. The gender medicine exception

In gender medicine, the same hormones — often at considerably higher doses — are prescribed to persons without any underlying endocrine pathology:

• A biological female reaches male testosterone levels, sometimes 10-20× her natural baseline.
• A biological male reaches female estrogen levels, combined with suppression of endogenous testosterone production.
• Initiation often follows an informed consent model, in some settings after a single consultation.
• Long-term effects are inadequately studied — the Cass Review² described the evidence base as "remarkably weak".
• In minors, physiological puberty is first suppressed — an intervention that occurs in no other medical context for healthy children.

4. Working with versus working against the body

Same-sex hormone replacement supports a system the body is designed for. Receptors, feedback loops, enzymes and target tissues are calibrated for the hormone in question. Cessation restores the natural state. Risks are primarily a function of dose and pre-existing comorbidity.

Cross-sex hormone administration does the opposite: exposure to a hormone the cellular architecture is not designed for, at levels exceeding the physiological range, with simultaneous suppression of endogenous production (anti-androgens, GnRH agonists). The effect reaches every tissue: bone, heart, muscle, brain, liver. A substantial proportion of these changes is irreversible.

5. The numbers

Cross-sex hormones demonstrably increase risk for:

• Thrombosis and stroke — estrogen in biological males raises VTE incidence by approximately 5-fold (Getahun 2018³).
• Cardiovascular morbidity — testosterone in biological females raises acute cardiovascular events (Nota 2019⁴).
• Osteoporosis — particularly when GnRH analogues preceded the therapy (Joseph 2019⁵).
• Infertility — frequently permanent; informed consent at a young age is often incomplete on this point.
• Long-term malignancy — only now coming into view as the first large cohorts have been followed long enough.

A 55-year-old man on substitution remains within physiological serum values. A biological female on transition therapy is at male levels — outside the range her tissues were designed for. The difference is categorical, not gradual.

6. The linguistic problem

7. International reassessment

The Cass Review (NHS, 2024), the Karolinska stop in Sweden (2021), the Finnish revision (Palveluvalikoima 2020) and the Pathways Trial at King's College London (2025) all point in the same direction: in gender medicine, the medical standard that governs mainstream endocrinology is not consistently applied. In these jurisdictions, first-line treatment for adolescents shifts to comorbidity-first assessment, watchful waiting and exploratory therapy; hormonal and surgical interventions have become exceptions rather than the rule.

8. The unanswered question

A biological body responds to a hormone in the same way, regardless of the indication. The risks of cross-sex hormones are logically greater, not smaller. Nevertheless, the precautionary principle that has governed mainstream hormone medicine since 2002 is systematically disregarded in gender medicine. The answer is not medical but political and ideological — and that is precisely where the international reassessment now under way finds its core.