Serum concentrations of prolactin, a trophic hormone produced by the pituitary gland, have been shown to be raised in certain group of patients with cancer. Prolactin was detected in 0-20% of the colon cancer by immunohistochemistry and in plasma in 6-53% of the patients. These conflicting results do not support the hypothesis of an ectopic prolactin production by colon carcinoma. The aim of this study was to confirm the reported incidence of hyper-prolactinemia in colorectal cancer and to find further evidence for an ectopic prolactin production by the tumor. Thirty consecutive patients with colon carcinoma were studied. Before surgery all the patients underwent blood sample collection to assay plasma prolactin levels. All patients underwent colectomy. All the neoplastic specimens were tested with antiprolactin antibody. In none of the patients were significantly high preoperative levels of plasma prolactin found. Prolactin immunostaining was not identified in any of the tumor specimens. We could not confirm previous reports of frequent hyperprolactinemia in patients with cancer. This is the first report in which the incidence of both hyperprolactinemia and prolactin positive immunostaining was 0%. Our study was unable to demonstrate the synthesis of prolactin by colorectal cancers. The tumor is unlikely to be the source of hormone production. Our results suggest that circulating prolactin levels cannot be used as prognostic marker in patients with colon cancer.

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