Recurrences of ACTH-secreting adenomas after pituitary adenomectomy can be accurately predicted by perioperative measurements of plasma ACTH levels

BACKGROUND: Adenomectomy is the treatment of choice for ACTH-secreting adenomas. Although the development of ACTH deficiency immediately after adenomectomy suggests surgical success, disease recurrence was reported in patients who developed hypocortisolism postoperatively. In the current study, we examined the value of measuring perioperative plasma ACTH and cortisol levels in predicting disease recurrence of patients with ACTH-secreting adenomas.

METHODS: Consecutive patients (n = 55; 41 females, 14 males) with clinical, biochemical, and histological documentation of ACTH-secreting adenomas were investigated after pituitary adenomectomy. All patients were followed with clinical monitoring and frequent measurements of plasma ACTH and serum cortisol levels, and none received glucocorticoids unless or until they developed symptoms of adrenal insufficiency or when their serum cortisol levels were ≤3 μg/dL.

RESULTS: Postoperative serum cortisol levels reached ≤3 μg/dL in 46 of 55 and were ≥4 μg/dL in the remaining 9. Simultaneously measured plasma ACTH levels in the latter 9 patients were >40 ng/L when the serum cortisol reached its nadir. In contrast, among the 46 patients who had serum cortisol levels of ≤3 μg/dL, plasma ACTH levels measured simultaneously were ≤20 ng/L in 38 of 46 and >20 ng/L in the remaining 8. During a mean follow-up period of nearly 7 years, patients who had a nadir plasma ACTH of >20 ng/L developed recurrences even though their postoperative serum cortisol levels were ≤3 μg/dL.

CONCLUSIONS: Despite profound hypocortisolemia after adenomectomy, a simultaneously measured plasma ACTH level of >20 ng/L in the perioperative period is highly predictive of future recurrence of ACTH-secreting adenomas.