THE PLASMA 11-HYDROXYCORTICOSTEROIDS RESPONSE TO INSULIN-INDUCED HYPOGLYCAEMIA IN CHILDREN AND ADOLESCENTS

Abstract

The insulin tolerance test (ITT) was performed in 102 children and adolescents belonging to the following 6 groups: controls (56 subjects), pituitary insufficiency (17 patients), delayed puberty (13 patients), obesity (6 patients), idiopathic precocious sexual development (6 patients) and congenital adrenal virilization (4 patients). All subjects showed hypoglycaemia. The mean percentage of maximal reduction in the blood sugar from the fasting concentration varied from 41 to 50 in all the groups. The control subjects and the patients with delayed puberty, obesity, precocious sexual development and congenital adrenal virilization showed an increase in plasma 11-hydroxycorticosteroids (11-OHCS) to a mean peak value ranging between 20 and 25 μg/100 ml, measured 60 min after the injection of insulin. From these results it was concluded that a rise in plasma 11-OHCS to a value of 20 μg/100 ml or more after hypoglycaemic stress denotes a normal corticotrophin releasing factor (CRF) and corticotrophin (ACTH) reserve. The patients with pituitary insufficiency showed 3 types of response independent of the degree of hypoglycaemia: nine patients showed a normal response, four had a medium response and four showed no response. There was a good correlation between lack of response of plasma 11-OHCS induced by hypoglycaemia and the urinary 17-OHCS response during the metopiron test, indicating that both these tests act at the hypothalamic level. Although the rise in plasma 11-OHCS after ITT was less marked than after the lysine vasopressin (LVP) test, it is suggested that the ITT is to be preferred as a clinical screening test, as it permits concomitant evaluation of both ACTH and growth hormone reserve. Another advantage of performing the ITT before the LVP test is that it allows of the diagnosis of a hypothalamic disturbance in ACTH secretion.