RT Journal Article SR Electronic T1 G470 Early medical treatment of gender dysphoria: baseline characteristics of a uk cohort beginning early intervention JF Archives of Disease in Childhood JO Arch Dis Child FD BMJ Publishing Group Ltd and Royal College of Paediatrics and Child Health SP A198 OP A198 DO 10.1136/archdischild-2015-308599.424 VO 100 IS Suppl 3 A1 HM Gunn A1 C Goedhart A1 G Butler A1 SN Khadr A1 PA Carmichael A1 RM Viner YR 2015 UL http://adc.bmj.com/content/100/Suppl_3/A198.1.abstract AB Aims To describe characteristics of patients referred early (<16 yrs) medical treatment for gender dysphoria (GD). GD is a rare condition in which individuals experience clinically significant distress due to incongruence between their psychological perception of, and their natally assigned, sex. Methods We collected data prospectively on all patients referred from May 2010––July 2014 for early pubertal suppression using gonadotropin – releasing hormone analogue (GnRHa) therapy. Results 61 young people (34 natal males; 55.7%) were referred for early intervention to the national GD service endocrine liaison clinic at mean age of 13.1 years (range 9.8–15.3). All patients had a karyotype consistent with their natal sex. More natal males were in early puberty (32.4% Tanner 1/2; n = 11) than natal females (11.1% Tanner 1/2; n = 3). Baseline endocrinology and physical examination were normal for natal sex in all patients. All females who had standard synacthen tests to exclude adrenal dysfunction (77.8%; n = 21) had normal cortisol and 17OHP. 38.2% (n = 13) males had low bone mineral density compared with 11.1% of females (n = 3). 50 patients (81.9%) elected to receive GnRHa following full explanation and informed consent at Tanner stage 3, following international guidelines. GnRHa could not be commenced immediately if pre-pubertal (10/61), having very low bone mineral density (3/61) or low body mass index (BMI) (2/61). All who began GnRHa achieved full gonadatropin suppression. No young people withdrew from GnRHa treatment in the first 2 years. Many GPs were unwilling to prescribe GnRHa (56.0%; n = 28/50) therefore local hospitals (8.0%; n = 4) or the tertiary centre (36.0%; n = 18) issued prescriptions. Conclusion Early medical intervention in GD with GnRH suppression of puberty is effective and well–tolerated. Assessment of growth, bone health and psychological outcomes will be important to assess the medium-and long-term safety and effectiveness of early intervention for GD.