Critical size of residual adrenal tissue and recovery from impaired early postoperative adrenocortical function after subtotal bilateral adrenalectomy

Background. Subtotal bilateral adrenalectomy may preserve adrenocortical function. Little is known about the early postoperative function of the adrenal remnant. Method. In 10 patients with bilateral adrenal tumors (pheochromocylomas, adrenocortical nodular hyperplasia, and adrenal metastases), plasma adrenocorticotropic hormone (ACTH), serum cortisol, and maximal cortisol liberation were examined with an ACTH lest after subtotal bilateral adrenalectomy, which left 15% to 30% of adrenal tissue in situ. Results. In the early postoperative period, all patients had normal basal serum cortisol levels (mean, 415 +/- 208 nmol/L; normal morning range, 138-690 nmol/L) but pathologically increased plasma ACTH levels (mean, 55 +/- 42 pmol/mL; normal, < 10.1 pmol/L). In 6 patients, a pathologic ACTH test result was observed. During follow-up (mean, 11.3 +/- 7.6 months), all patients were found to have a normal ACTH test result. None of the patients required steroid supplementation. However, in patients with both familial pheochromocytoma and impaired adrenocortical function during the early postoperative period, the maximal increase of serum cortisol after ACTH stimulation was significantly,reduced (mean, 301 +/- 86.8 nmol/L) compared with control subjects (mean, 490 +/- 132.6 nmol/L; P = .019). Conclusion. After subtotal bilateral adrenalectomy left 15% to 30% of adrenal tissue in situ,functional recovery could be observed in all patients. However, subclinical impairment of the adrenocortical function with questionable clinical significance has to be considered in some of the patients. Especially during the early postoperative period, careful observation of the patients without exogenous steroid administration is required.