The low-dose ACTH test does not identify mild insufficiency of the hypothalamnic-pituitary-adrenal axis in children with inadequate stress response

A systematic review and meta-analysis of Synacthen tests for assessing hypothalamic-pituitary-adrenal insufficiency in children

BACKGROUND

The diagnostic value of tests used in assessing hypothalamic-pituitary-adrenal axis (HPA) in children remains controversial.

DESIGN

A systematic review and meta-analysis with receiver-operated-characteristic curve was undertaken to assess the diagnostic values of conventional standard dose 250 μg tetracosactrin (ACTH), short Synacthen test (SSST) and/or low-dose Synacthen test (LDSST) in the assessment of HPA insufficiency in children. Studies eligible for inclusion were any study that compared the use of the LDSST and/or SSST in the assessment of central adrenal insufficiency in children compared with reference standard test.

RESULTS

There were no randomised trials found. SSST resulted in higher specificity and positive likelihood ratio than LDSST. The LDSST had a higher sensitivity (86% vs 61%) but a lower specificity (88% vs 99%) than the SSST, but there was high heterogeneity from the LDSST studies with various doses of Synacthen used.

CONCLUSIONS

Lack of standardisation of assays and protocols with regard to timing, frequency and dose has resulted in diagnostic inaccuracies. There is no clear evidence to indicate that LDSST is superior to SSST in the assessment of HPA axis in children. The choice of either SSST or LDSST should be individualised based on clinical judgement for each patient. This systematic review has identified the need for a well-designed, adequately powered, randomised controlled trial on the use of diagnostic tests used in assessing HPA axis in children.

[How to manage the interruption of a treatment with anti-inflammatory corticosteroids?]

A prolonged treatment with anti-inflammatory corticosteroids induces an inhibition of ACTH secretion from pituitary corticotroph cells. An abrupt interruption of such a treatment potentially leads to the risk of an acute adrenal failure, in particular in stressing situations. The inertia in reactivation of the secretion of the stimulating hypothalamic factors (CRH and AVP) and consecutively of ACTH can be responsible for an inability to adapt the secretion of glucocorticoids in response to stress. A short-time treatment (<3 weeks) with anti-inflammatory corticoids does not expose to this risk. On the contrary, a more prolonged treatment, especially with high daily doses, needs to perform an evaluation of the level of corticotroph secretion. This evaluation should be done before to consider that either stopping the treatment is out of risk or if the initiation of a substitutive treatment with hydrocortisone is required. The measurement of morning plasma cortisol level already provides a significant information. As to whether that is needed, a dynamic evaluation can be performed. Among the available tests, the Synacthen(®)test, easy to perform and using at best 1μg of β1-24 ACTH, appears the most finely informative to answer this question and to choose the most adapted follow-up.

Requirement for age-specific peak cortisol responses to insulin-induced hypoglycaemia in children

OBJECTIVE

Based on adult data, a peak cortisol response ≥500 nmol/l to insulin-induced hypoglycaemia constitutes a normal. Age-specific reference ranges for basal morning cortisol have been developed for clinical use in the paediatric population. Such reference ranges are not clearly established for peak cortisol responses to insulin-induced hypoglycaemia despite limited data suggesting an effect of age on peak cortisol. The aims of this study were to assess factors affecting the cortisol response to insulin-induced hypoglycaemia in children and to determine whether the peak cortisol response was related to age.

DESIGN

The present study was a retrospective cohort study.

METHODS

Retrospective analysis of children and adolescents aged ≤18 years undergoing the insulin tolerance test with adequate hypoglycaemia was undertaken. Patients with hypopituitarism or severe hypothalamic-pituitary-adrenal axis impairment (peak cortisol value <400 nmol/l) or using systemic glucocorticoids were excluded.

RESULTS

Two hundred and twenty-three tests were analysed. Peak cortisol responses ≥500 nmol/l occurred in 183 (82%) tests. Age was negatively associated with peak cortisol responses (r=-0.15, P=0.03). A peak cortisol response <500 nmol/l was significantly less common in patients aged <12 years (9/97 (9%) vs 31/126 (25%); P=0.004). In children aged <12 years, the median (5th-95th centiles) peak cortisol values were 610 (480-806) nmol/l compared with 574 (442-789) nmol/l in children aged ≥12 years (P<0.004). Similarly, median cortisol increment was significantly higher in younger patients (301 nmol/l compared with 226 nmol/l (P=0.0004)).

CONCLUSIONS

Use of a single peak cortisol threshold in children of all ages is not appropriate and will result in overdiagnosis of adrenal insufficiency in adolescents.

Lack of sensitivity of the 1-μg low-dose ACTH stimulation test in a paediatric population with suboptimal cortisol responses to insulin-induced hypoglycaemia

CONTEXT

The insulin-tolerance test (ITT) is the gold standard for evaluation of the hypothalamic-pituitary-adrenal (HPA) axis. The low-dose ACTH stimulation test is increasingly used for evaluation of secondary adrenal insufficiency as several studies performed in adults have demonstrated high sensitivity and specificity when compared to the ITT. Whether the ACTH stimulation test demonstrates similar sensitivity in a paediatric and adolescent population compared with the gold standard is unclear.

OBJECTIVE

To compare the sensitivity of the low-dose (1-μg) Synacthen(™) test (LDSST) and the gold-standard ITT in a paediatric and adolescent population.

DESIGN AND PATIENTS

A retrospective review of 42 consecutive LDSSTs in children and adolescents with suboptimal cortisol responses (peak <500 nm) on ITT.

RESULTS

Thirty-one patients (74%) had an adequate cortisol response to low-dose Synacthen(™) (sensitivity 26%). Patients had a higher cortisol increment with the LDSST than ITT (median Δ cortisol 294 vs 168 nm, P < 0.0001) and correspondingly a higher cortisol peak (median peak cortisol 572 vs 396 nm, P < 0.0001). Patients who had a suboptimal peak cortisol both on ITT and on LDSST had a lower baseline cortisol on ITT (median 178 vs 227 nm, P = 0.04). Peak cortisol on ITT was significantly higher in patients who had a subsequent normal LDSST than those that did not (median 417 vs 300 nm, P = 0.0005).

CONCLUSIONS

The 1-μg LDSST lacks sensitivity in detection of secondary adrenal insufficiency in children when compared to the gold-standard ITT.

Overnight ACTH-cortisol dose responsiveness: comparison with 24-h data, metyrapone administration and insulin-tolerance test in healthy adults

OBJECTIVE

To estimate the dose dependence of endogenous ACTH stimulation of adrenal cortisol secretion overnight.

DESIGN

Ten-minute sampling for ACTH and cortisol over 8 and 24 h (n = 17), after metyrapone administration (n = 6), during an insulin-tolerance test (n = 7).

SUBJECTS

Healthy adults.

MEASUREMENTS

ACTH dose-responsive estimates.

RESULTS

Twenty-four hour ACTH-cortisol concentration pairs yielded an estimated EC(50) (one-half maximally stimulatory ACTH concentration) of 5·1 (2·2-9·5) pmol/l [median (range)]. This did not differ from EC(50) s based on 8- or 6-h data [5·9 (3·5-11) and 7·5 (3·7-41) pmol/l] in the same individuals. ACTH efficacy (maximally stimulatable cortisol secretion rate) was 8·4 (3·1-20), 11 (5·9-24) and 15 (5·9-22) nmol/l/min, when calculated over 24, 8 and 6 h, respectively (P = NS). Adrenal sensitivity (slope term) was also consistent across sampling durations, viz. 14 (1·3-95), 18 (1·3-64) and 20 (1·3-64) slope units. Compared with placebo, metyrapone reduced ACTH efficacy from 11 (6·2-62) to 2·8 (1·5-4·5) nmol/l/min for cortisol (n = 9, P < 0·001), while increasing ACTH efficacy for 11-desoxycortisol from 2·3 (0·9-2·9) to 99 (70-218) nmol/l/min (n = 6, P < 0·01), thus affirming face validity. Combined ACTH and cortisol responses to hypoglycaemia allowed an estimate of ACTH efficacy of 28 (22-81) nmol/l/min, compared with the control value of 8·7 (5·6-26), suggesting enhanced adrenal responsiveness.

CONCLUSIONS

The results suggest that endogenous ACTH-adrenal drive can be approximated from overnight 8-h sampling of paired ACTH and cortisol concentrations. This strategy may have merit in clinical research in childhood, pregnancy, anxiety states and frail elderly individuals, when ACTH injections are not desired.