Objectives: Bilateral adrenalectomy may be indicated in patients with Cushing's disease in whom hypercortisolism is not resolved after pituitary microsurgery. However, Nelson's syndrome is a major long-term complication of such therapy. We have carried out a longitudinal study on patients with Cushing's disease who underwent bilateral adrenalectomy comparing plasma beta-lipotrophin (beta-LPH) with ACTH levels.
Patients and methods: Seven patients unsuccessfully treated by pituitary surgery for Cushing's disease underwent bilateral adrenalectomy. Blood samples were collected on days 8 and 15 and at 1, 2, 3, 6, 9, 12, 18 and 24 months after adrenalectomy in all patients. Five patients were followed up for the longer periods of 30, 33, 39, 72 and 84 months respectively. Plasma ACTH and beta-LPH were determined by RIA after extraction. Pituitary CT scan was done at 6-8 month intervals.
Results: A pituitary tumour was detected in three patients at 14, 24 and 26 months after adrenalectomy respectively. The basal ACTH (range 8-21 pmol/l) began to rise between 15 and 30 days and exhibited a sharp increase with a range of 36-114 pmol/l at 3 months and a range of 53-187 pmol/l at 6-9 months after adrenalectomy. The ACTH levels in the three patients who later presented with a pituitary tumour were indistinguishable from those observed in the other patients up to 12 months after adrenalectomy. Only at 12 months or thereafter were their ACTH levels higher than in the other patients (958 +/- 252 vs 205 +/- 22 pmol/l). beta-LPH concentrations changed in parallel with ACTH levels. The ACTH levels correlated positively with beta-LPH levels (r = 0.76).
Conclusions: In patients with Cushing's disease undergoing bilateral adrenalectomy, plasma ACTH and beta-LPH concentrations cannot predict the development of pituitary tumours until 12 months after surgery.