Effect of an OT antagonist on the control of the midcycle LH surge in women.
OBJECTIVE
Data in women regarding the role of OT in LH secretion during the LH surge are conflicting. As in previous studies blood samples for LH measurements were taken infrequently, we re-examined this matter in women with a fully characterized midcycle LH surge.


METHODS
Normal women were studied over two cycles. When the dominant follicle reached a diameter of either 16-17 mm (Group 1) or 18-19 mm (Group 2), the women were infused intravenously for 3 h with normal saline (cycle-1) or atosiban (cycle-2).


METHODS
Fifteen women (10 in group 1 and 5 in group 2) aged 23-35 years.


METHODS
Blood samples were obtained every 6 h to characterize the midcycle LH surge.


RESULTS
The time interval (mean +/- SEM) from the start of the infusion to the onset of the LH surge in the two cycles was 46.8 +/- 4.8 and 45.6 +/- 9.6 h in group 1 and 6.0 +/- 2.4 and 7.5 +/- 2.8 h, respectively, in group 2. LH values during the LH surge were similar in the two cycles except in group 1 at the point of 30 h at which LH value in cycle-2 (41.2 +/- 4.6 mIU/ml) was significantly lower than in cycle-1 (52.8 +/- 3.4 mIU/ml, P < 0.05). Nevertheless, in each group, the area under the curve for LH was similar in the two cycles.


CONCLUSIONS
Antagonism of endogenous OT action by atosiban does not alter the LH profile during a fully characterized midcycle LH surge, suggesting that OT is not a major regulator of LH secretion in women.
Vanakara
P
P
Department of Obstetrics and Gynaecology, Medical School, University of Thessalia, Larissa, Greece.
Dafopoulos
K
K
Papastergiopoulou
L
L
Kallitsaris
A
A
Papageorgiou
I
I
Messinis
I E
IE
D000328:Adult; D005260:Female; D006727:Hormone Antagonists / Q000008:administration & dosage*; D006801:Humans; D007986:Luteinizing Hormone / Q000378:metabolism*; D006080:Ovarian Follicle / Q000187:drug effects / Q000378:metabolism*; D010121:Oxytocin / Q000037:antagonists & inhibitors*; D014668:Vasotocin / Q000008:administration & dosage / Q000031:analogs & derivatives*; D055815:Young Adult
D006727:Hormone Antagonists; C047046:atosiban; D010121:Oxytocin; D007986:Luteinizing Hormone; D014668:Vasotocin