Effects of melatonin on uterine hypertrophy/hyperplasia: A preliminary experimental rat study

Endometrial hyperplasia is a process of endometrial proliferation that results in a thickening of the endometrial tissue. Melatonin might be able to change the pathophysiological process and prognosis into a positive way that might prevent and heal endometrial hyperplasia, which is the first stage of endometrial cancer. For this perspective, we tried to investigate the effect of melatonin on uterine hypertrophy/hyperplasia in an experimental rat model. Forty Wistar-Albino rats were undergone bilateral oophorectomy and randomized into four groups. To create a model of uterine hypertrophy/hyperplasia in all groups, except the control group [C] (n = 10), 4 mg/kg/day estradiol hemihydrate were given for 14 days. The uterine hypertrophy/hyperplasia was evaluated histopathologically in the left uterine horns, then the groups were treated for 14 days as follows; melatonin (10 mg/kg/day/po) [M] (n = 10), melatonin + estradiol hemihydrate (10 mg/kg/day/po and 4 mg/kg/day/po) [M + E] (n = 10), and dark environment [D] (n = 10). Finally, the effects of the melatonin were examined histopathologically in the right uterine horns. An uterine hypertrophy/hyperplasia model was established in all groups compared to the control group (p < 0.05). In the [M] and [M + E] groups, epithelial cell height and luminal epithelial cell height significantly decreased (41μm vs 12μm, p = 0.005; 14μm vs 10μm, p = 0.005, respectively for [M] group) and (32μm vs 14μm, p = 0.012; 17μm vs 10μm, p = 0.017, respectively for [M + E] group). The [D] group exhibited a significant decrease in epithelial cell height (33μm vs 20μm, p = 0.017). With or without estrogen exposure, melatonin-treated and physiologically melatonin-released rats experienced a significant uterine hypertrophy/hyperplasia recovery. Melatonin may have protective effects on endometrial hyperplasia.