Rr. Shankar et al., TESTING THE HYPOTHALAMIC-PITUITARY-ADRENAL AXIS IN SURVIVORS OF CHILDHOOD BRAIN AND SKULL-BASED TUMORS, The Journal of clinical endocrinology and metabolism, 82(6), 1997, pp. 1995-1998
The objective of this study was to determine whether a low dose of ACT
H (0.2 mu g/kg) improves the sensitivity of ACTH testing in detecting
hypothalamic-pituitary-adrenal (HPA) axis abnormalities in survivors o
f childhood brain and skull-based tumors. Twenty-two children who had
undergone treatment for brain or skull-based tumors were enrolled in a
prospective study to extensively evaluate the HPA axis. Five tests of
the adrenal axis were evaluated in each patient, including determinat
ion of basal serum cortisol, a standard ACTH test (250-mu g iv bolus),
a low dose ACTH test (0.2 mu g/kg iv bolus), an insulin tolerance tes
t, and a single dose metyrapone test. Cortisol responses to both ACTH
tests were nearly identical. Two patients (9%) failed the low dose ACT
H test, whereas three (14%) failed the standard ACTH test; five of the
children (23%) failed the insulin tolerance test, and five (23%) had
abnormal responses to metyrapone. One child who initially passed the m
etyrapone test failed the test 19 months later after becoming symptoma
tic. All children with abnormal metyrapone test results had low levels
of basal cortisol secretion. In this study, the low dose ACTH test di
d not improve the sensitivity of ACTH testing for evaluation of the HP
A axis. We conclude that a single morning basal cortisol level is a go
od screen for testing the HPA axis in children. We recommend confirmin
g HPA axis dysfunction with the single dose metyrapone test, although
this test also has limitations.