Cortisol responses to the insulin hypoglycaemia test in children.
OBJECTIVE
To determine the timing of the peak cortisol response to the insulin hypoglycaemia (IH) test in children and to establish paediatric reference data.


METHODS
We retrospectively reviewed all IH tests in a tertiary paediatric endocrine referral centre over a 6-year period. Inclusion criteria were age <16 years and adequate hypoglycaemia (glucose < or =2.0 mmol/l). Patients with an impaired hypothalamic-pituitary-adrenal axis or receiving glucocorticoid medication were excluded. Fifty-four subjects (35 males) met the criteria. Blood samples were collected at -30, 0, 20, 30, 60, 90, 120, and 150 min in relation to insulin bolus injection (0.15 U/kg) at 0 min. Glucose, cortisol, and growth hormone (GH) were measured in all samples.


RESULTS
Peak cortisol and GH responses occurred by 90 min in all subjects. Peak cortisol was inversely correlated with age (rs -0.65, p<0.0001). The median (5th centile) peak cortisol value was 689 nmol/l (547 nmol/l) in children younger than 10 years as compared with 555 nmol/l (468 nmol/l) in those older than 10 years (p<0.0001). Peak cortisol was not related to peak GH (rs -0.20, p=0.15).


CONCLUSIONS
Blood sampling in the IH test may be curtailed 90 min after injection. The peak cortisol response to IH is age related.
Crofton
P M
PM
Department of Paediatric Biochemistry, Royal Hospital for Sick Children, Edinburgh, UK. patricia.crofton@luht.scot.nhs.uk
Don-Wauchope
A C
AC
Bath
L E
LE
Kelnar
C J H
CJ
D017677:Age Distribution; D002648:Child; D002675:Child, Preschool; D005260:Female; D019382:Human Growth Hormone / Q000097:blood / Q000378:metabolism*; D006801:Humans; D006854:Hydrocortisone / Q000097:blood / Q000378:metabolism*; D007003:Hypoglycemia / Q000097:blood* / Q000503:physiopathology; D007223:Infant; D007328:Insulin; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D012016:Reference Values; D012189:Retrospective Studies
D007328:Insulin; D019382:Human Growth Hormone; D006854:Hydrocortisone