EFFECTS OF OOPHORECTOMY AND ESTROGEN-TREATMENT ON BASAL LEVELS AND 24-H PROFILES OF OXYTOCIN

The regulation of oxytocin is incompletely understood and data indicat e that in addition to several neurotransmitters, estrogens may be invo lved. The aim of the present study was to investigate the effects of o ophorectomy and hormonal replacement therapy (HRT) on basal levels and 24-h profiles of oxytocin. Basal levels of oxytocin were measured in 95 women who had undergone hysterectomy and who were divided into thre e groups: group A (n = 30), oophorectomized (BSO), not on HRT; group B (n = 32), BSO, receiving HRT; and group C (n = 33), ovaries preserved and not receiving HRT. The 24-h profiles of oxytocin were measured in nine women before and after hysterectomy. Continuous venous blood sam pling was performed 1 week before surgery and 6-7 weeks after surgery for all nine women. Thereafter, three of the four oophorectomized wome n started replacement therapy with transdermal estradiol 50 mug/day. A fter 10 weeks of treatment, a third sampling was performed. Exogenous estrogen administration was associated with increased oxytocin levels and negative correlation between oxytocin and follicle stimulating hor mone/luteinizing hormone levels was found. Removal of the ovaries did not reduce oxytocin levels in any of the investigated groups. When 24- h values were analyzed, no specific rhythmic or pulsatile pattern befo re or after hysterectomy, with or without simultaneous oophorectomy, w as found.