Evidence that oxytocin is a physiological component of LH regulation in non-pregnant women.
BACKGROUND
Regulation of the LH surge is central to the functioning of the female ovulatory cycle. In animal models, oxytocin has been shown to alter LH activity. Oxytocin advanced the LH surge and, conversely, oxytocin receptor antagonists inhibited full production of the LH surge in rats. Few data exist on the possibility that oxytocin modulates LH in women.


METHODS
Ten non-pregnant women participated in this study over two menstrual cycles. One cycle was a control cycle, and the other a trial cycle; the two were separated by at least one cycle. When the diameter of an ovarian follicle was >15 mm, a subject was allocated at random into either a control or treatment group. In a control cycle, volunteers received normal saline; in a treatment cycle, volunteers received an oxytocin antagonist (atosiban).


RESULTS
For treatment cycles, the maximum LH concentration was significantly less than that in control cycles (42.1 +/- 6.2 versus 60.3 +/- 8.3 IU/l respectively; P < 0.05). Maximum FSH and estradiol concentrations were not significantly different between the two groups.


CONCLUSIONS
The results indicated that inhibition of endogenous oxytocin affects the endocrinology of the ovulatory cycle in women, and strongly suggest that oxytocin has a role in the physiological processes of LH regulation.
Evans
J J
JJ
Department of Obstetrics and Gynaecology, Christchurch School of Medicine and Health Sciences, Christchurch, New Zealand. john.evans@chmeds.ac.nz
Reid
R A
RA
Wakeman
S A
SA
Croft
L B
LB
Benny
P S
PS
D000328:Adult; D005260:Female; D005498:Follicular Phase / Q000187:drug effects / Q000502:physiology*; D006727:Hormone Antagonists / Q000008:administration & dosage; D006801:Humans; D007986:Luteinizing Hormone / Q000097:blood*; D010121:Oxytocin / Q000502:physiology*; D014668:Vasotocin / Q000008:administration & dosage / Q000031:analogs & derivatives*
D006727:Hormone Antagonists; C047046:atosiban; D010121:Oxytocin; D007986:Luteinizing Hormone; D014668:Vasotocin