Gradual recovery of lactotroph responsiveness to dynamic stimulation following surgical removal of prolactinomas: Long-term follow-up studies

Abstract

Prolactin-secreting pituitary adenomas were selectively removed through a transsphenoidal approach from 120 women. Basal serum PRL levels (measured one to six months after surgery) were normal in 96 patients and decreased appreciably but not to normal in the remaining 24 patients. Dynamics of PRL secretion were studied at three to four months in 81 patients who had normal basal PRL level. Two different patterns of response to provocative stimuli were noted in these patients. In one group (group I, n = 65), patients had >100% rise in serum PRL following TRH or perphenazine (Pz) administration. However, when analyzed as a group, the mean ± SEM incremental responses (ΔPRL) to TRH and Pz in these patients (29.9 ± 1.9, 20.4 ± 1.5 ng/mL) were significantly less ( P < 0.005 and P < 0.001) than those of normal women (38.8 ± 5, 33 ± 5 ng/mL, respectively). Nineteen of these patients were restudied 12 to 72 months after surgery. The responses to provocative stimulation at that time were improved and similar to normal women. In contrast, in the second group (n = 16) of patients (group II), the responses to stimulation with the same agents were blunted or absent and remained so during subsequent studies. Recurrence of the hyperprolactinemia was noted in 11 of the 16 patients in group II and in only two of 65 patients in group I. The daily serum PRL levels in the immediate postoperative period were higher in patients from group II than those from group I. We conclude that transsphenoidal surgery is an optimal form of therapy for patients with PRL-secreting adenomas. The dynamics of PRL secretion are helpful in evaluating the outcome of surgery and in predicting patients at risk for recurrences. Following complete removal of the adenoma, lactotrophs of the normal pituitary recover gradually and their responsiveness to stimulation becomes normal months to years later. These findings are consistent with the concept that PRL-secreting pituitary adenomas are primary pituitary disorders.