Background: Conventional hydrocortisone dosing schedules do not mimic the normal circadian rhythm of cortisol making it difficult to optimise treatment in congenital adrenal hyperplasia (CAH).

Case Details: We report a 14.5 year old boy with CAH who had reduced bioavailability (42% (normal 80% orally and 100% by intramuscular route) and increased clearance (half-life 50 mins (normal range 70–100 mins) of oral doses of hydrocortisone leading to ambient serum 17 hydroxyprogesterone (17OHP) concentrations of 400 nmol/l (14.5 ng/ml) and androstenedione concentrations of 24.9 nmol/l (7.1 ng/ml).

Intervention: Using a continuous but variable subcutaneous hydrocortisone infusion (CSHI) via an insulin pump rapid control of his CAH was attained with a normal cortisol circadian profile. Average daily hydrocortisone dose was 17.4–18.6 mg/m² which produces on average 24h serum cortisol and 17OHP concentrations of 316 nmol/l (115 ng/ml) and 4.3 nmol/l (1.4 ng/ml) respectively. Therapy has been maintained over 4 years with suppression of normal adrenal androgen production and normal progression through puberty.

Conclusions: CSHI may prove a valuable adjunct to therapy for CAH particularly in patients requiring high doses or oral hydrocortisone and in those with abnormal hydrocortisone pharmacokinetics.