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Timing of peak serum cortisol values in preterm infants in low-dose and the standard ACTH tests
R Karlsson1, J Kallio, J Toppari
1Department of Pediatrics, University of Turku, Finland. rikka.karlsson@utu.fi
Insights
The low-dose adrenocorticotropic hormone (ACTH) test in infants shows peak cortisol levels at 30-40 minutes. This timing differs from the standard ACTH test, aiding in adrenal insufficiency evaluation.
Area of Science:
- Pediatric Endocrinology
- Endocrinology
- Biochemistry
Background:
- The low-dose ACTH test is increasingly favored for evaluating adrenal suppression in both infants and adults.
- However, the concentration-time profile of plasma cortisol following a low-dose ACTH stimulation in infants remains unclear.
- This is particularly relevant given the frequent use of glucocorticoids in neonates.
Purpose of the Study:
- To compare the timing of peak plasma cortisol values between the low-dose and standard ACTH stimulation tests in preterm and full-term infants.
- To establish optimal blood sampling times for the low-dose ACTH test in this population.
Main Methods:
- A crossover study design was employed in 10 infants (26-40 weeks gestational age).
- Infants underwent both standard (250 microg/1.73 m2) and low-dose (1 microg/1.73 m2) ACTH stimulation tests.
- Serum cortisol concentrations were measured by radioimmunoassay (RIA) at 0, 30, 40, 60, and 120 minutes post-administration.
Main Results:
- In the low-dose ACTH test, peak cortisol levels were observed at 30 or 40 minutes in 9 out of 10 infants.
- In contrast, peak levels in the standard-dose ACTH test occurred at 60 or 120 minutes in 8 out of 10 infants.
- These findings are consistent with observations in adult populations.
Conclusions:
- For the low-dose ACTH test in infants, blood sampling should be performed prior to dosing and between 30 and 40 minutes post-dosing.
- This timing optimizes the detection of peak cortisol response, aiding in the assessment of adrenal function in neonates.
- The study provides crucial pharmacokinetic data for the low-dose ACTH test in pediatric populations.
Abstract:
The low-dose ACTH test seems to reveal mild cases of adrenal insufficiency and is beginning to be preferred over the standard ACTH test in the evaluation of adrenal suppression both in infants and in adults. The concentration-time profile of plasma cortisol in infants after a low ACTH dose is obscure. In this crossover study, we compared timing of the peak values in the low-dose and the standard ACTH stimulation tests in preterm and full-term infants. We performed the standard ACTH tests (250 microg/1.73 m2) and the low-dose ACTH tests (1 microg/1.73 m2) on 10 infants (26-40 wk gestational age) and measured serum cortisol concentration at 0, 30, 40, 60, and 120 min by RIA. Nine of the infants had received postnatal glucocorticoid treatment, and most of them had also been treated with dexamethasone antenatally. In the low-dose test, the peak values occurred at 30 or 40 min in 9/10 patients. In the standard-dose test, the peak values occurred at 60 or 120 min in 8/10 patients. These results are comparable with those from adults. According to this study, blood samples for the low-dose ACTH test in infants should be taken before dosing and between 30 and 40 min after dosing.