Serum prolactin in patients with hypothalamus and pituitary disorders

Serum prolactin concentrations were studied in 115 patients with anatomically defined disorders in the hypothalamo-pituitary region. Fifty of the patients had expansively growing pituitary adenomas; in 17 of them (13 females and four males) the prolactin values were slightly raised (15 to 100 microgram/liter), and in 13 (11 females and two males) they were over 100 microgram/liter. The frequency of elevated prolactin values was higher for females than for males. Fifteen patients with invasively growing pituitary adenomas had very high serum prolactin levels (range 1230 to 31,500 microgram/liter). In a single case of malignant pituitary adenoma, the serum prolactin was at the lower level of detection. Of 49 further patients with suprasellar meningiomas, craniopharyngiomas, or other expansive or destructive lesions of the hypothalamus and sellar region, 15 had slightly raised prolactin values (maximum 114 microgram/liter). Eight of these 49 patients had sellar destruction, with a roentgenological picture similar to that in patients with invasive pituitary adenomas. Among these eight patients, the maximum prolactin value was 67 microgram/liter. It is concluded that moderately raised serum prolactin values (up to 100 microgram/liter) in a patient with a sellar tumor does not prove that the tumor is a prolactinoma. A serum prolactin value of 100 to 1000 microgram/liter strongly indicates a prolactin-producing tumor. In a patient with sellar destruction, a serum prolactin value of over 1000 microgram/liter is proof that the destruction is caused by an invasive pituitary adenoma.