Inhibins (INH) are dimeric glycoproteins, composed of an alpha-subunit (INH-α) and one of two possible beta-subunits (INH-βA or -βB), with substantial roles in human reproduction and in endocrine-responsive tumors. The aims of this study were to determine the frequency and tissue distribution of INH-α, -βA and -βB in normal and malignant endometria. Samples were obtained from normal (n=46), atrophic (n=8) and endometrioid carcinoma tissue (EC; G1=93; G2=32; G3=14). INH-α was significantly higher in normal compared to malignant endometrial tissue, showing a cyclical variation throughout the menstrual cycle. EC G3 did not express this subunit. INH-βA and -βB showed specific staining reactions within the tumor cells. The highest intensity of INH-βA was observed in the normal secretory phase compared to adenocarcinomas (p<0.05). For INH-βB, the significantly highest expression was noted in EC G3 compared to EC G2 (p<0.05) and atrophic endometrial tissue. In conclusion, INH-α, -βA and -βB were immunolabeled in normal and malignant endometria. INH-α was expressed in a declining relationship in the transition from normal to tumor tissue, suggesting a tumor suppressive function in EC. A high expression of INH-βB was observed in EC G3 compared to G2, suggesting an important role in the progression of endometrial carcinogenesis. However, the utilization of these subunits as specific tumor markers still remains unclear.

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