Prolactin dynamics and tumour size in the prediction of surgical outcome for prolactinoma

Each of 62 females were studied for a period of between two and 72 months (mean 36 months) following the removal of a prolactinoma by transsphenoidal pituitary surgery. Our aims were to define the relationships between pre- and post-operative features, the operative findings and the functional outcome. Pre-operative serum prolactin (PRL) concentrations correlated with tumour diameter (r = 0.55, p less than 0.001). Following surgery two groups of patients were identified: Group 1, 46 spontaneously and regularly menstruating patients and Group 2, 16 patients with persistent amenorrhoea. The patients in Group 1 had significantly lower pre-operative and post-operative serum (PRL) concentrations (p less than 0.02 and p less than 0.001 respectively) and significantly greater PRL responses to thyrotrophin releasing hormone (TRH) and metoclopramide stimulation after surgery (p less than 0.001). There was not a significant difference in tumour size between the groups. Forty-four (96 per cent) of the patients in Group 1 had normal post-operative serum PRL concentrations within one week of surgery. By comparison (p less than 0.001) only 42 and 20 per cent respectively of Group 1 patients who were tested had normal TRH and metoclopramide evoked PRL secretion following surgery. Return of regular menstruation was associated with cessation of galactorrhoea in 44 patients (96 per cent) and ovulation occurred in 37 of 38 menstruating patients for whom data are available. All patients with normal TRH and metoclopramide stimulation tests menstruated spontaneously. Nevertheless most patients who menstruated did so in spite of retaining suppressed PRL responses. Of 46 patients followed to date whose serum PRL was normal one week after surgery, seven later were found to have an elevation of serum PRL outside the normal range but in only two has this been persistent. We suggest that a single measurement of serum PRL one week following transsphenoidal pituitary surgery for prolactinoma provides a good basis for deciding about the future management of patients who desire menstruation and pregnancy.