Protocol › Age criteria · Last reviewed 2026-05-16

Age criteria and Tanner stages

Summary

The original Dutch Protocol set thresholds at Tanner stage 2 (about 11–12 years) for puberty suppression, 16 for cross-sex hormones and 18 for surgery. The Endocrine Society guideline of 2017 maintained these benchmarks but allowed hormones to begin before age 16 in selected cases, with documented consent of the patient and parents.

1. Tanner stages

The Tanner stages (1962) describe the progression of sexual maturation. The Dutch Protocol uses the Tanner stage as a criterion for starting GnRH agonists:

Tanner	Feature girls	Feature boys	Age (mean)
1	Prepubertal	Prepubertal	< 10–11
2	Beginning breast development (thelarche)	Testicular volume 4 ml+	10–12
3	Further breast development, pubic hair	Voice change begins	12–13
4	Breast development almost complete	Facial hair	13–15
5	Adult	Adult	15+

2. Original age thresholds

Intervention	Minimum criterion	Source
GnRH agonist	Tanner 2 (~12 years)	Delemarre 2006
Cross-sex hormones	16 years	Delemarre 2006
Surgery	18 years	Delemarre 2006

3. Adjustments under Endocrine Society 2017

The Endocrine Society in its revised guideline (2017) allowed cross-sex hormones to start "earlier than 16 years" in selected cases, on the basis of "compelling reasons" and with consent of patient and parents.¹ This relaxation was criticised by various later authors as a deviation from the original Dutch design; see WPATH SOC and the Dutch Protocol.

4. Application in later international practice

In UK GIDS practice GnRH agonists were in some cases prescribed after only one diagnostic appointment and at ages down to about 10 years.² This deviation from the Dutch criteria is a central concern in the Cass Review (2024). Finland (COHERE 2020) and the UK have applied age thresholds more strictly since 2020.

Critical note

The age thresholds used are not based on empirical research into the optimal start age, but on pragmatic clinical considerations (pubertal stage, legal majority). SBU (2022) and Cass (2024) note that there are no comparative studies indicating whether, for example, Tanner 3 or 4 — a later start — would yield different outcomes. The Tanner 2 threshold in practice means that many adolescents are treated well before sexuality and abstract reasoning have developed.³