OBJECTIVE: To estimate trends in use and outcomes of progestin therapy for premenopausal patients with endometrial intraepithelial neoplasia. METHODS: The MarketScan Database was used to identify patients aged 18-50 years with endometrial intraepithelial neoplasia from 2008 to 2020. Primary treatment was classified as hysterectomy or progestin-based therapy. Within the progestin group, treatment was classified as systemic therapy or progestin-releasing intrauterine device (IUD). The trends in use of progestins and the pattern of progestin use were examined. A multivariable logistic regression model was fit to examine the association between baseline characteristics and the use of progestins. The cumulative incidence of hysterectomy, uterine cancer, and pregnancy since initiation of progestin therapy was analyzed. RESULTS: A total of 3,947 patients were identified. Hysterectomy was performed in 2,149 (54.4%); progestins were used in 1,798 (45.6%). Use of progestins increased from 44.2% in 2008 to 63.4% in 2020 ( P =.002). Among the progestin users, 1,530 (85.1%) were treated with systemic progestin, and 268 (14.9%) were treated with progestin-releasing IUD. Among progestin users, use of IUD increased from 7.7% in 2008 to 35.6% in 2020 ( P <.001). Hysterectomy was ultimately performed in 36.0% (95% CI 32.8-39.3%) of those who received systemic progestins compared with 22.9% (95% CI 16.5-30.0%) of those treated with progestin-releasing IUD ( P <.001). Subsequent uterine cancer was documented in 10.5% (95% CI 7.6-13.8%) of those who received systemic progestins compared with 8.2% (95% CI 3.1-16.6%) of those treated with progestin-releasing IUD ( P =.24). Venous thromboembolic complications occurred in 27 (1.5%) of those treated with progestins; the venous thromboembolism (VTE) rate was similar for oral progestins and progestin-releasing IUD. CONCLUSION: The rate of conservative treatment with progestins in premenopausal individuals with endometrial intraepithelial neoplasia has increased over time, and among progestin users, progestin-releasing IUD use is increasing. Progestin-releasing IUD use may be associated with a lower rate of hysterectomy and a similar rate of VTE compared with oral progestin therapy.