〔Abstract〕 Objective To investigate the fluctuations in serum uteroglobin-related protein 1 (UGRP1) levels in hashimoto’s thyroiditis (HT) patients before and after pregnancy, and to analyze the influencing factors. MethodsTen healthy individuals and ten HT patients were enrolled. Thyroid fine needle aspiration cytology combined with immunohistochemistry was used to detect the expression of UGRP1 protein in thyroid cells between the two groups. A total of 30 healthy women were enrolled as the control group, and 149 HT patients were recruited, including 36 non-pregnant HT patients, 77 pregnant HT patients and 36 post-partum HT patients. According to levothyroxine sodium (L-T4) administration status, the pregnant HT group was further subdivided into the non-L-T4 subgroup ( n=36) and the L-T4 subgroup ( n=41). Kruskal-Wallis H test was used to compare the general clinical data, thyroid-related indicators and serum UGRP1 levels among groups. Spearman correlation analysis and univariate linear regression analysis were performed to explore the influencing factors of serum UGRP1 levels in HT patients. ResultsUGRP1 expression was negative in thyroid cells of all healthy individuals, while 80% of HT patients exhibited positive expression. The serum UGRP1 levels in the control group, non-pregnant HT group, pregnant HT group, and post-partum HT group were 359.52 (297.84, 440.60), 695.77 (518.55, 865.04), 207.96 (173.82, 264.91), and 582.08 (280.83, 735.87) pg/mL, respectively, with statistically significant differences among groups ( P<0.001). Correlation analysis showed no significant correlation between serum UGRP1 levels and thyroid-related indicators or gestational age in pregnant HT patients. Univariate linear regression analysis revealed that pregnancy status was negatively correlated with serum UGRP1 levels in HT patients ( β=-424.457, P<0.001), while L-T4 administration had no statistically significant effect on serum UGRP1 levels in pregnant HT patients ( P=0.890). ConclusionSerum UGRP1 levels are significantly higher in HT patients than in healthy individuals. Pregnancy is an important factor affecting serum UGRP1 levels in HT patients, which can lead to a decrease in UGRP1 levels, while L-T4 administration has no significant effect on serum UGRP1 levels.