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Michael J O'Grady, Conor Hensey, Miriam Fallon, Hilary Hoey, Nuala Murphy, Colm Costigan and Declan Cody

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.

Free access

Rikke Beck Jensen, Ajay Thankamony, Susan M O'Connell, Jeremy Kirk, Malcolm Donaldson, Sten-A Ivarsson, Olle Söder, Edna Roche, Hilary Hoey, David B Dunger and Anders Juul

Background

Short children born small for gestational age (SGA) are treated with a GH dose based on body size, but treatment may lead to high levels of IGF1. The objective was to evaluate IGF1 titration of GH dose in contrast to current dosing strategies.

Methods

In the North European Small-for-Gestational-Age Study (NESGAS), 92 short pre-pubertal children born SGA were randomised after 1 year of high-dose GH treatment (67 μg/kg per day) to three different regimens: high dose (67 μg/kg per day), low dose (35 μg/kg per day) or IGF1 titration.

Results

The average dose during the second year of the randomised trial did not differ between the IGF1 titration group (38 μg/kg per day, s.d. 0.019) and the low-dose group (35 μg/kg per day, s.d. 0.002; P=0.46), but there was a wide variation in the IGF1 titration group (range 10–80 μg/kg per day). The IGF1 titration group had significantly lower height gain (0.17 SDS, s.d. 0.18) during the second year of the randomised trial compared with the high-dose group (0.46 SDS, s.d. 0.25), but not significantly lower than the low-dose group (0.23 SDS, s.d. 0.15; P=0.17). The IGF1 titration group had lower IGF1 levels after 2 years of the trial (mean 1.16, s.d. 1.24) compared with both the low-dose (mean 1.76, s.d. 1.48) and the high-dose (mean 2.97, s.d. 1.63) groups.

Conclusion

IGF1 titration of GH dose in SGA children proved less effective than current dosing strategies. IGF1 titration resulted in physiological IGF1 levels with a wide range of GH dose and a poorer growth response, which indicates the role of IGF1 resistance and highlights the heterogeneity of short SGA children.