Ultrastructural morphometry of prolactin secreting adenomas treated with dopamine agonists

19 macroprolactinomas and 1 microprolactinoma were analysed by light microscopical, immunohistological and ultrastructural as well as morphometrical methods. 8 adenomas were removed from patients who were treated preoperatively with bromocriptine and/or Lisurid for different periods. 18 of 20 adenomas were positive for PRL on the immunohistological level. One case was negative. This patient showed a good response to the pharmacological treatment. The ultrastructure of this case revealed many secretory granules. A morphometric analysis of the ultrastructure could be performed in 19 cases; 1 case had to be excluded because of large necrotic areas. The following qualitative significant alterations after the treatment could be established: Reduction of the volume density of the rough endoplasmatic reticulum; Reduction of the size of the granula diameter; Increase of the volume density of the more irregular and indented nuclei. Other alterations were as follows: Reduction of the nuclear size; Increase of the number of secretory granules and of the volume density of lysosomes. These changes were to be observed in most of those tumors which responded to the dopamine agonist treatment. The non-responding adenomas and one which was removed 6 days after having discontinued a successful preoperative medical therapy were similar to the untreated adenomas. The results display the influence of dopamine agonist on the hormone synthesis, release and degradation in PRL secreting adenoma cells.