Pituitary apoplexy in patients with Nelsons syndrome has rarely been described. We report the case of a 33-year-old woman with a history of bilateral adrenalectomy for Cushings disease three years previously. Following adrenalectomy, despite adequate replacement therapy with prednisone and fludrocortisone, she became hyperpigmented, morning serum ACTH level rose from 185 to over 1250 pg/ml (normal range 1060) and the pituitary tumour increased from 0.8/0.3 to 1.3/0.8 cm on computerized tomography scans. Before starting radiosurgery, the patient became pregnant. She presented at 22 weeks with sudden onset of severe headache and nausea, blood hypotension, with no visual field defects or consciousness impairment. A pituitary magnetic resonance imaging study showed a 1.6 cm intrasellar mass suggesting pituitary apoplexy. Conservative treatment with dexamethasone has been started, with favorable evolution. One month later, while the patient had resumed her usual replacement treatment, the morning serum ACTH was 63 pg/ml, thyroid hormones, thyrotropin, prolactin and gonadotropins were normal, and a 4 to 6 l polyuria was noted which normalized on oral desmopressin. Serial ultrasonography showed normal foetal development and the pregnancy went uneventfully afterwards. Although the clinical picture was typical for a pituitary apoplexy within the ACTH-secreting tumour, the association with diabetes insipidus may also suggest lymphocytic hypophysitis in this rare patient with Nelsons syndrome and pregnancy.