Isolated glucocorticoid deficiency.

A three-month-old boy with hypoglycemic episodes, feeding problems and hyperpigmentation is described. Hormone assays revealed elevated serum ACTH values and low levels of plasma cortisol that did not rise after exogenous ACTH administration; blood pressure, serum electrolytes and earlier plasma aldosterone and renin activity were in the normal range. These data suggest a diagnosis of an isolated glucocorticoid deficiency, secondary to unresponsiveness to ACTH. Replacement therapy with glucocorticoids was highly effective. Despite replacement therapy, during follow-up he had an increase in basal plasma renin activity with aldosterone concentration normal. In our patient, a mineralcorticoid deficiency might eventually develop; therefore, the selective glucocorticoid deficiency might also be part of a progressive defect involving the glomerulosa too.