Altered osmotic thresholds for arginine vasopressin secretion and thirst during superovulation and in the ovarian hyperstimulation syndrome (OHSS): relevance to the pathophysiology of OHSS.
OBJECTIVE
To test the hypothesis that decreases in and maintenance of a new steady state in plasma osmolality and sodium level in ovarian hyperstimulation syndrome (OHSS) are due to altered osmoregulation of arginine vasopressin secretion and thirst.


METHODS
Prospective study.


METHODS
IVF-ET program in a university-based assisted reproductive treatment center.


METHODS
Eight women undergoing superovulation for IVF-ET and five women with normal menstrual cycles.


METHODS
Two-hour infusion of 5% saline on day 3 or 4 after hCG administration in patients undergoing IVF or in the early luteal phase in controls. A 5% saline infusion test was done on day 10 after hCG administration in one patient with OHSS and one patient without OHSS, both of whom were undergoing IVF.


METHODS
Comparison of changes in thresholds for thirst and plasma vasopressin to plasma osmolality. Changes in urine osmolality, plasma electrolytes, hemoglobin level, and hematocrit were assessed at baseline and during infusion of 5% saline.


RESULTS
The sensitivity of the changes in arginine vasopressin secretion and thirst after 5% saline infusion was similar in IVF patients on day 3 or 4 after hCG and controls. However, the osmotic threshold was significantly lower by 6 mOsm/kg in IVF patients. By day 10 after hCG, the lower osmotic thresholds for arginine vasopressin secretion and thirst persisted in OHSS, although the sensitivity to arginine vasopressin secretion was markedly reduced.


CONCLUSIONS
The osmotic thresholds for arginine vasopressin secretion and thirst are reset to lower plasma osmolality during superovulation for IVF-ET. This new lower body tonicity is maintained until at least day 10 after hCG in OHSS. Decreases in plasma osmolality and plasma sodium levels in OHSS are due to altered osmoregulation rather than electrolyte losses; correction of apparent "electrolyte imbalance" in OHSS is therefore inappropriate.
Evbuomwan
I O
IO
Reproductive Medicine, International Centre for Life, Newcastle upon Tyne, United Kingdom. ievbuomawan@talk21.com
Davison
J M
JM
Baylis
P H
PH
Murdoch
A P
AP
D000328:Adult; D001127:Arginine Vasopressin / Q000097:blood / Q000378:metabolism*; D002712:Chlorides / Q000097:blood; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D005260:Female; D005307:Fertilization in Vitro / Q000009:adverse effects; D006400:Hematocrit; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D009997:Osmotic Pressure; D016471:Ovarian Hyperstimulation Syndrome / Q000097:blood / Q000503:physiopathology*; D011446:Prospective Studies; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage; D012964:Sodium / Q000097:blood*; D013480:Superovulation / Q000502:physiology*; D013894:Thirst / Q000502:physiology*
D002712:Chlorides; D006063:Chorionic Gonadotropin; D006454:Hemoglobins; D012462:Saline Solution, Hypertonic; D001127:Arginine Vasopressin; D012964:Sodium