Nelson's syndrome following partial pituitary microadenomectomy and pregnancy.

We report for the first time the development of Nelson's syndrome in a patient who had previously undergone unsuccessful pituitary microadenomectomy and subsequently bilateral adrenalectomy. The removal of a 3-mm portion of a microadenoma did not protect against the development of Nelson's syndrome within 3 years which was closely related to pregnancy, a previously noted association. This report suggests that the development of Nelson's syndrome depends not on the size of the initial pituitary tumour but rather on its individual potential for proliferating once free of the inhibitory effects of glucocorticoid excess.