The low dose synacthen test: experience in well preterm infants

Area of Science:

• Neonatal endocrinology
• Pediatric adrenal function testing

Background:

• Assessing adrenal function in preterm infants is crucial for monitoring their health.
• Previous studies established a normal response threshold using a higher dose of ACTH (36 µg/kg).

Purpose of the Study:

• To determine normal adrenal response criteria for the low-dose synacthen test in well preterm infants.
• To evaluate if existing criteria from higher-dose ACTH tests are applicable to physiological doses.

Main Methods:

• A pilot study involving seven well preterm infants.
• Administration of a low dose of ACTH (500 ng/1.73 m²).
• Measurement of peak serum cortisol levels post-administration.

Main Results:

• The minimum peak serum cortisol observed was 358 nmol/L.
• 6 out of 7 infants achieved peak cortisol levels ≥360 nmol/L.
• 71% of infants showed a cortisol increment of ≥200 nmol/L from baseline.

Conclusions:

• The established criterion of a peak serum cortisol ≥360 nmol/L for normal adrenal response is applicable to the low-dose synacthen test in preterm neonates.
• This suggests a consistent threshold for assessing adrenal function regardless of ACTH dosage in this population.