Inadequate cortisol response to the tetracosactide (Synacthen®) test in non-classic congenital adrenal hyperplasia: an exception to the rule?

AIMS: To describe cortisol response to tetracosactide and to review the literature on adrenal function in non-classic congenital adrenal hyperplasia (NCCAH) patients. METHODS: We compared cortisol responses to tetracosactide (250 µg) between NCCAH patients and a comparison group (CG) of patients with premature pubarche and normal tetracosactide test. An adequate cortisol response was defined as a peak ≥18 µg/dl. RESULTS: We included 35 NCCAH patients (26 girls, 9 boys), whose mean age at testing was 7.0 years (0.8-15.6), and 47 patients in the CG (39 girls, 8 boys), whose mean age was 7.2 years (0.5-9.9). Baseline cortisol was significantly higher in the NCCAH group than in the CG [12.9 (4.3-22.2) vs. 9.7 (4.2-16.2) µg/dl, respectively; p = 0.0006]. NCCAH patients had lower cortisol peak response compared to the CG [18.2 (6.3-40) vs. 24.9 (12-30.3) µg/dl, respectively; p < 0.0001]. Peak cortisol was <18 µg/dl in 21/35 (60%) NCCAH patients versus 1/47 (2.1%) in the CG. No NCCAH patients had acute adrenal insufficiency, but 2 reported severe fatigue that improved with hydrocortisone. CONCLUSIONS: The cortisol response to tetracosactide was inadequate (<18 µg/dl) in 60% of patients with NCCAH. Hydrocortisone therapy may deserve consideration when major stress (surgery, trauma, childbirth) or objectively documented fatigue occurs in NCCAH patients with inadequate cortisol response.