Endometrial T2 values and thickness measured during the spontaneous menstrual cycle: potential imaging biomarker related to female physiological hormones

The endometrium undergoes morphological and functional changes during menstrual cycles, regulated by female hormones. MRI T2 weighted imaging (T2WI) plays an essential role in endometrial disease evaluation. This study aims to define the cyclic course of endometrial T2 values and thickness and explore their relationship with basal female sex hormones. We prospectively recruited 38 healthy volunteers (20–30 years:22; 30–40 years:16), 3.0 T MR were performed during the menstrual phase (MP), follicular phase (FP), peri-ovulation phase (OP), and luteal phase (LP). Basal serum oestradiol (E), progesterone (P), luteinizing hormone (LH) and follicle stimulating hormone (FSH) hormone was tested. Endometrium thicknesses, T2 values were obtained in each phase. Pearson correlation test, Fisher's least significant difference (LSD) test, the analysis of variance (ANOVA) test, and the paired sample t test were applied. The endometrium thickness was significantly thinner in the younger age group (p < 0.001). The thickness was significantly thinner in first half compared with that in the second half in both groups (p < 0.001). Endometrial T2 values were significantly shorter in menstrual cycles compared with the other three phases (p ≤ 0.001). Both endometrial T2 value and thickness were correlated to female hormones. Basal FSH and P were correlated with T2 values in the menstrual phase in the 30–40 year group. Serum FSH was correlated with endometrial thickness. T2 mapping and endometrium thickness distinguish in different cyclic phases, provided background information for evaluation pathologic conditions. Moreover, with their correlations with female basal sex hormones, we found the T2 mapping sequence can provide a potential biomarker for quantifying the endometrium's physiological status. The current study is the first to investigate the relationship between T2 values and basal sex hormones. This new technique may find a role in determining endometrium functions such as receptivity and might have potential clinical significance in the diagnosis of endometrium-related gynecology diseases.