Study Objective. To investigate the effects of gonadotropin-releasing hormone (GnRH) analog pretreatment on endometrial Na+, K+-adenosine triphosphatase (ATPase) pump function and peripheral blood vasopressin levels, and their role in fluid absorption and mechanisms of hyponatremia in patients undergoing hysteroscopic endometrial ablation.
Design. Prospective, randomized, placebo-controlled study (Canadian Task Force classification I).
Setting. University-affiliated hospital.
Patients. Seventeen women with dysfunctional uterine bleeding.
Intervention, Nine women received a GnRH analog and eight received saline approximately 6 to 8 weeks before hysteroscopic ablation by electrosurgery.
Measurements and Main Results. Both before randomization and immediately before surgery, endometrial biopsy samples were obtained and numbered consecutively without patient identification. Operative hysteroscopy was performed with glycine 1.5% mixed with 2% alcohol. The amount of irrigant and irrigant deficit; blood levels of albumin and ethanol; hematocrit and hemoglobin; changes in sodium levels; and central venous pressure were compared. The Na+, K+-ATPase pump activity was significantly increased in the GnRH analog group compared with the saline group and correlated with decreased estradiol levels (0.4 +/- 0.08 vs 0.26 +/- 0.06 mu mol/min/ml). Vasopressin levels were significantly lower in the GnRH group (3.2 +/- 0.9 vs 7.6 +/- 1.7 mu mol/L). Mean volume of irrigant used and operating time were similar in both groups. Volume deficit, decrease in protein, and hematocrit were less in GnRH than in the saline group. Blood ethanol levels, decrease in sodium, and irrigant deficit were significantly lower in GnRH group.
Conclusion. Pretreatment with GnRH analogs may prevent the adverse effects of estradiol on endometrial Na+, K+-ATPase and creates a protective mechanism against iatrogenic hyponatremia, which is more critical in women than men in case of absorption of irrigating fluid. Moreover, created hypoestrogenism may enhance Na+, K+-ATPase activity in brain as well as endometrium, thus decreasing women's susceptibility to hyponatremic complications and brain damage. Suppressed vasopressin levels may be protective against fluid absorption in GnRH analog-treated patients.