Objectives: Patients with prolactinomas and patients with acromegaly often have heterogenous adenomas. In this study we have focused on patients with prolactinomas who developed acromegaly and acromegalic patients with hyperprolactinaemia. Our hypothesis is that some patients with hyperprolactinaemia may develop clinical acromegaly.

Methods: We have included patients examined at department M, Odense University Hospital between 1996 and 2001. Seventy-eight patients with prolactinomas, 65 females and 13 males, with a median age (range) of 30 Years (14-74) and 47 Years (20-66), respectively, were included in the study.

Results: In females and males the median prolactin (PRL) levels were 90 microg/l (27-4700; normal values (NV) <or=23) and 1075 microg/l (24-6500; NV <or=14), respectively. The PRL levels were significantly higher in males compared with females (P<0.002). Fifty-nine patients with acromegaly, 24 females and 35 males, with a median age (range) of 45 Years (24-70) and 53 Years (19-70), respectively, were included. Seven of the 24 females had hyperprolactinaemia, with PRL levels of 90 microg/l (27-494). Thirteen of the 35 males had hyperprolactinaemia with PRL levels of 47 microg/l (17-251). Three females with prolactinomas developed acromegaly clinically and biochemically. These patients had a normal low GH level and/or a normal IGF-I level at first diagnosis.

Conclusions: Our findings suggest that there is a common group of patients with a pituitary adenoma who secrete PRL and GH unsynchronously. Some of these patients have clinical acromegaly at diagnosis and some patients diagnosed as prolactinomas will develop acromegaly. We suggest an annual IGF-I measurement as a screening test.