Normal cortisol response on low-dose synacthen (1 microg) test in children with Prader Willi syndrome.

Introduction: It has been postulated that central adrenal insufficiency (CAI), resulting from hypothalamic dysfunction, may contribute to the increased unexplained death rates in Prader Willi syndrome (PWS). A study using the overnight metyrapone test reported a 60% prevalence of CAI in children with PWS. We used a low-dose Synacthen test to screen for CAI in children with PWS.
Methods: We studied 41 children with genetic diagnosis of PWS [20 males; mean age, 7.68 (±5.23) yr] in five pediatric endocrinology centers in Australasia. All participants were randomly selected, and none had a history of Addisonian crisis. Ten of the cohort were receiving sex hormone therapy, 19 were receiving GH, and four were receiving T4. Their mean body mass index z-score was +1.48 (±1.68). Baseline morning ACTH and cortisol levels were measured, followed by iv administration of 1 μg Synacthen. Post-Synacthen cortisol levels were measured at 30 min, and a cortisol level above 500 nmol/liter was considered normal.
Results: The mean baseline ACTH and cortisol were 15 (±14) ng/liter and 223 (±116) nmol/liter, respectively. The mean 30-min plasma cortisol was 690 (±114) nmol/liter, and the average increase from baseline was 201%.
Conclusions: Our result suggests that CAI is rare in children with PWS.