Evaluation of secondary adrenal insufficiency: Findings by corticotropin-releasing hormone test and magnetic resonance imaging in parallel

Background. The corticotropin-releasing hormone (CRH) stimulation test is reliable for diagnosing pituitary or hypothalamic adrenal insufficiency. In the present study, we evaluated secondary adrenal insufficiency in patients with pituitary disease by CRH test and magnetic resonance imaging (MRI). Methods. A total of 12 healthy persons and 20 patients with pituitary disorder were recruited, including 6 with Sheehan's syndrome, 6 with idiopathic panhypopituitarism, 3 with isolated ACTH deficiency, 2 with pituitary apoplexy, 2 with empty sella syndrome and 1 with postoperative suprasellar tumor. Blood ACTH and cortisol levels were measured after 100 μg ovine CRH (oCRH) intravenous bolus infusion. Results. In patients, basal ACTH was 15.9 ± 17.3 pg/ml and basal cortisol was 4.8 ± 4.6 μg/dl. These values were significantly lower than those in controls (p = 0.02). In 11 of 20 patients (3 with Sheehan's syndrome, 3 with panhypopituitarism, 2 with empty sella, 2 with isolated ACTH deficiency and 1 with pituitary apoplexy), a delayed and prolonged ACTH response was observed. In the other 9 patients, ACTH showed little change. In all patients, there was no apparent increase in cortisol value. Moreover this value was significantly lower than in healthy persons (6.2 ± 5.4 vs. 21.1 ± 6.0 μg/dl; p < 0.0001). Sellar MRI showed complete empty change in all Sheehan's syndrome, apoplexy and empty sella syndrome patients. The six patients with panhypopituitarism had variable hypoplastic adenohypophysis with or without visible pituitary stalk. The three isolated ACTH deficiency cases demonstrated a normal anatomy. Conclusions. Our study showed that patients with pituitary disease had significantly lower plasma cortisol response after oCRH than controls. Thus, CRH testing appears useful for the diagnosis of central adrenal insufficiency. The two different functional ACTH responses to CRH observed in each pituitary disorder did not correlate with damage levels shown on MRI.