Relationship between sonographic endometrial thickness and progestin-induced withdrawal bleeding

Objective: To determine whether the response to the progestin challenge test can be predicted from the endometrial thickness measured sonographically. Methods: Progestin challenge tests were performed on 44 women with secondary amenorrhea, each of whom also had her endometrial thickness measured by transvaginal ultrasonography and her serum estradiol (E2) levels determined. The relationships between the response to the challenge test, endometrial thickness, and serum E2 levels were studied, as well as whether the presence or absence of withdrawal bleeding could be predicted from the endometrial thickness and serum E2 levels. Results: The endometrium was significantly thicker in 32 women who had withdrawal bleeding (10.3 +/- 4.1 mm) than in the 12 who did not bleed (5.0 +/- 1.3 mm) (P < .001). The serum E2 level was also significantly higher in the positive group: 45.3 +/- 19.4 versus 18.6 +/- 8.0 pg/mL (P < .001). Endometrial thickness of 6.0 mm or more predicted the occurrence of withdrawal bleeding with an accuracy of 95.5%. Endometrial thickness was superior to the serum E2 level in predicting withdrawal bleeding. Conclusion: Progestin-induced withdrawal bleeding can be predicted from the endometrial thickness measured sonographically.