Hypoinsulinemia in a patient with isolated ACTH deficiency

We report on a patient with isolated ACTH deficiency accompanying deficient insulin response to glucose. The subject is a 59 year-old male. He was admitted to our hospital because of a hypoglycemic attack. Urinary excretion of 17-hydroxycorticosteroid (17-OHCS) and 17-ketosteroid (17-KS) was low. Plasma ACTH levels decreased and serum cortisol levels were undetectable. ACTH did not respond to CRF stimulation for three consecutive days. Antibodies to At-T 20 cells (anterior pituitary cell-derived cell line) were positive in the serum of this patient. Serum immunoreactive insulin (IRI) levels were not detected throughout the day. The urinary excretion of C-peptide decreased to 9.8 micrograms/day. IRI responses on 75 g oral glucose tolerance test (OGTT) were examined at one and two months after the start of cortisol supplementation. No remarkable IRI response was observed, although blood glucose levels were maintained within the normal range. Eight months after the start of cortisol supplementation, the insulin response to 75 g OGTT appeared. The present study suggests that the recovery from hypo-insulinemia may be delayed even after normalization of serum cortisol levels in ACTH deficiency. This may be possibly due to the salutary effects of cortisol in maintaining plasma insulin levels. The time lag may be due to other factors also.