Context: In congenital adrenal hyperplasia (CAH), elevation of adrenal androgens leads to accelerated growth and bone maturation with compromised adult height.

Objective/Patients: To analyze retrospectively early growth and bone maturation in 17 untreated simple virilising (SV) CAH patients.

Setting: Radboud University Nijmegen, Medical Centre

Interventions: Growth data were collected until time of diagnosis. Height was expressed as height SD score (HSDS) and corrected for target height (HSDS-THSDS). Bone maturation was determined and expressed as bone age acceleration (BA_c)_.

Main outcome measures: Growth pattern and bone maturation before the diagnosis.

Results: In the term group (n = 11) there was no increase in HSDS-THSDS in the first year of life (-0.1 SD/year; 95% C.I. -0.5, 0.3) with a consecutive significant (P < 0.001) increase up to 0.9 SD/year (95% C.I. 0.7, 1.0). In the premature group (n = 3) there was a catch up growth of 1.6 SD/year (95% C.I. 0.9,2,3) in the first year followed by a growth of 1.1 SD/year (95% C.I. 0.9, 1.5) in the following years. There was a positive linear correlation between BA_c and age of diagnosis (r = 0,8).

Conclusion: Height velocity and bone maturation are not increased in untreated children with mild forms of SV CAH in the first year of life. After this period there is a progressive increase in height velocity and bone maturation in strong relation to the duration of androgen exposition. This observation has implications for the dose of glucocorticoids to be used in SV CAH patients in the first year of life.