The ectopic secretion of prolactin by nonpituitary tumors has been reported to occur in only two patients, and that by a single investigator. The apparent rarity of this occurrence may be due to its actual infrequency, or to failure to recognize hyperprolactinemia, or to the circulation of the hormone in a form with low biological activity.Because of the high incidence of elevated hormone levels in the blood of patients with cancers, and the frequency with which prolactin is found in tumor tissue extracts, the authors attempted to ascertain the frequency of hyperprolactinemia in patients with a variety of cancers.Serum samples from 215 patients were screened. Ninety of these patients had melanoma, 23 had cancer of the colon and rectum, 20 had cancer of the breast, 18 had non-Hodgkin's lymphoma and sarcoma, 14 had lung cancer, 8 had Hodgkin's disease, and 42 had other types of cancer. The mean prolactin value for the 33 normal subjects in this study was 8.3 ng, with two standard deviations above the mean being 16.5 ng/ml. The mean values of all the groups of cancer patients were above the mean value of the normal control subjects, but because of the large standard deviations of each group, these differences were not statistically significant.Prolactin levels were borderline elevated (20 to 25 ng/ml, which is three standard deviations above the mean of the 33 normal subjects in this study, but less than two standard deviations above the mean of the authors' entire normal population) in 10 patients, and definitely elevated (above 25 ng/ml) in 15. The charts of the patients with borderline levels revealed that three had received irradiation to the chest, one had received irradiation to the head, and others were taking various drugs. Only two patients with melanoma had not received any therapy that could account for the elevated levels of prolactin; renal and thyroid function were normal in both.Fifteen patients had elevated prolactin levels ranging from 25.5 to 89.0 ng/ml. Five of them had received irradiation to the chest, two had received irradiation to the head, nine were taking phenothiazines for nausea and vomiting from chemotherapy, and three were taking opiates for pain. In one patient, the hyperprolactinemia was first noted following total neuroaxis irradiation after partial resection of a cerebellar medulloblastoma, and the hyperprolactinemia resulted in galactorrhea and amenorrhea. Sellar tomography in this patient showed the floor to slant to the left; erosion was present anteriorly on the left, compatible with the presence of a prolactin-secreting microadenoma. Bromocriptine therapy resulted in normalization of prolactin levels, cessation of galactorrhea and restoration of menses in this patient. Only three patients had hyperprolactinemia prior to any therapy, and they had no known cause for that condition. Renal and thyroid functions were normal in all three.In the patient with melanoma, additional serum samples revealed normal prolactin levels. Additional serum samples in the patient with lung cancer (squamous cell) also showed prolactin levels to be in the 30 to 40 ng/ml range. Paper and Sephadex G-100 column chromatog-raphy of125l-labeled prolactin incubated with aliquots of serum from these two patients did not reveal any excessive or unusual degradation of the labeled prolactin when compared to incubation in the serum of a normal subject.The authors conclude that there is no definitive evidence that prolactin is secreted by a tumor or that such ectopically secreted prolactin could cause any clinical symptom.
展开▼
