Aims. To detect aromatase expression in the endometrium of myomatous uteri and to correlate it with the location of the myoma, phase of the menstrual cycle, the presence of menorrhagia and oral contraceptive use.

Method. Aromatase p450 expression was measured using immunohistochemical methods in the endometrium of 116 patients. Sixty-one patients had menorrhagia associated with intramural/submucous myomas and nine had subserous myomas and no excessive bleeding. Forty-six patients had no uterine pathology and served as controls. Nineteen out of 61 patients with menorrhagia were oral contraceptive users at the time of the examination. Endometrial samples were obtained by hysteroscopy in all cases.

Results. Aromatase p450 expression was detected more frequently in the eutopic endometrium of patients with submucous or intramural myomas than in those in the subserous group, and was significantly greater during the proliferative phase than during the luteal phase or following the use of oral contraceptives. In normal uteri, aromatase expression was detected in the endometrium in less than 10% of users.

Conclusions. Aromatase expression in the endometrium was affected by the location of the myoma, the presence of symptoms, and the phase of the menstrual cycle. Oral contraceptives, on the other hand, inhibited aromatase expression in the eutopic endometrium of patients with submucous/intramural myomas.