Reliability of the low dose synacthen test in children undergoing pituitary function testing

Area of Science:

• Pediatric Endocrinology
• Endocrine Diagnostics
• Adrenal Function Testing

Background:

• Limited data exist on normal pediatric cortisol responses to the 1 microg low dose synacthen test (LDST).
• Assessing adrenal reserve in children requires reliable stimulation test parameters.

Purpose of the Study:

• To evaluate cortisol responses in children presumed to be normal during anterior pituitary function tests (APFTs) using the LDST.
• To determine the accuracy and potential false positive rate of the LDST in a pediatric population.

Main Methods:

• Retrospective analysis of LDST results in children with short stature and normal growth hormone.
• Cortisol levels were assessed post-stimulation, with peak levels compared against established criteria.

Main Results:

• A significant false positive rate of 21% was observed, with 7 out of 33 children showing suboptimal cortisol responses (<500 nmol/l).
• Repeat LDST in three children yielded normal results, suggesting transient or test-related abnormalities.
• Peak cortisol response demonstrated an inverse correlation with age (r = -0.44, p < 0.05).

Conclusions:

• The LDST in children exhibits a notable false positive rate (21%), indicating that one in five tests may not meet normal criteria.
• Clinicians should consider this high false positive rate when interpreting pediatric LDST results to prevent the overdiagnosis of adrenal insufficiency.