Endometrial expression of vasopressin, oxytocin and their receptors in patients with primary dysmenorrhoea and healthy volunteers at ovulation

Objective: To investigate gene expressions for neurohypophyseal and ovarian hormones as well as their receptors in the endometrium of women with primary dysmenorrhoea and healthy subjects at ovulation. Study design: A group of eight women with moderate to severe dysmenorrhoea and eight healthy subjects were compared in parallel between 18 and 35 years of age, regularly menstruating, non-overweight and nulliparous. The study was performed at The Department of Obstetrics and Gynecology, University Hospital of Lund, Sweden. Endometrial biopsies were taken around the time of ovulation, which was determined by repeated ultrasound examinations. Receptor and gene expressions for oxytocin and vasopressin in the tissue were measured. Results: The gene expression for oxytocin receptor was significantly lower in dysmenorrhoic than in healthy women, in median 1.21 and 3.44 oxytocin-receptor/actin, respectively (p = 0.048). The expressions for oxytocin peptide, vasopressin V_1a receptor, oestrogen receptor α, β and progesterone receptor did not differ between the two groups. Expression of vasopressin peptide was not detectable. Conclusion: A lower oxytocin receptor gene expression at mid-cycle could be involved in the aetiology of primary dysmenorrhoea. However, the importance of a paracrine effect of oxytocin and its receptor at ovulation warrants further investigation.