The human endometrium undergoes a unique process of benign angiogenesis under the control of ovarian steroids during reproductive life. Aberrant angiogenesis has been implicated in idiopathic menorrhagia, a common gynaecological complaint. One of the key factors involved in endometrial angiogenesis is adrenomedullin (AM), a multifunctional 52-amino acid peptide. AM mediates the activities of endometrial angiogenesis via calcitonin receptor-like receptor (CLR). The objective of the present study was to compare the endometrial expression of AM and CRL in women with and without idiopathic menorrhagia. Endometrial biopsies were obtained from 9 women with menorrhagia (>= 80 ml per menstruation) and 12 women with normal blood loss (<80 ml per menstruation). Protein and mRNA expression levels of AM and CLR were determined using immunohistochemistry and real-time PCR. Compared to the controls, patients with menorrhagia exhibited low immunostaining intensity of AM, while high CLR staining was observed in the epithelium (p<0.05). No difference in mRNA expression was observed between the groups. These data suggest that an imbalance in the AM/CLR system might alter endometrial angiogenesis in menorrhagia.