Objective:To investigate the level change of serum total n-terminal propeptide of type Ⅰ precollagen (t-PINP) /type Ⅰ collagen carboxy-terminal peptide (beta-CTX) ratio, 25-hydroxyvitamin D (25-hydroxyvitamin D, 25 (OH) ) ratio, and 25-hydroxyvitamin D in elderly women with differentiated thyroid cancer (DTC) after surgery and its value in the prevention and treatment of osteoporosis (OP) .Methods:From Jan. 2020 to May. 2021, 112 elderly female postoperative DTC patients treated with thyroid stimulating hormone (TSH) suppression in Department of Endocrinology of Wenzhou Hospital of Integrative Medicine were collected for a prospective study, and the incidence of OP after 1 year of treatment was counted, and according to the incidence of OP, they were divided into incidence group ( n=78) and non-incidence group ( n=34). The general information, thyroid parameters [TSH, free triiodothyronine (FT3), free thyroxine (FT4) ], bone mineral density (BMD), and serum t-titrosine (BMD) were compared between the two groups. SPSS22.0 software was used, and the counting data was described by examples χ2 test. Grade data was expressed in u, Ridit test was used, measurement data was described in mean±standard deviation ( ±s), t test was used, Pearson correlation coefficient model was used to analyze postoperative thyroid index and serum t-PINP/β- Correlation between CTX ratio and 25 (OH) D level, and serum t-PINP after 1 year of treatment was analyzed through interaction/β- The role of CTX ratio and 25 (OH) D level in OP occurrence. Results:The incidence of OP after 1 year of TSH suppression treatment in 112 elderly female post-DTC patients in this study was 69.64% (78/112) ; serum TSH levels (0.63±0.19) mIU/ml after 1 year of treatment in patients who developed OP were lower than those in patients who did not develop OP (0.81±0.22) mIU/ml, and serum FT3 (6.15±1.71) pmol/ml and FT4 levels (24.63±4.28) pmol/ml were higher than those of patients without OP (4.32±1.29) pmol/ml and (20.36±3.70) pmol/ml ( t1=4.391, t2=5.581, t3=5.050,all P<0.05) .Serum t-PINP/β-CTX ratio (130.27±18.09) and 25 (OH) D level (20.18±4.15) ng/ml after 1 year of treatment in patients with OP were lower than those in patients without OP (148.56±20.37) and (23.36±4.36) ng/ml ( t1=4.733, t2=3.672, both P<0.05) ; serum TSH levels were positively correlated with serum t-PINP/β-CTX ratio and 25 (OH) D levels, and serum FT3 and FT4 levels were negatively correlated with serum t-PINP/β-CTX ratio and 25 (OH) D levels after 1 year of treatment in patients with OP ( P<0.05) ; low serum t-PINP/β-CTX ratio after 1 year of treatment expression, and low 25 (OH) D levels showed a positive interaction in OP occurrence in a superphase multiplicative model ( P<0.05) . Conclusion:Serum t-PINP/β-CTX ratio and 25 (OH) D level are closely associated with the occurrence of OP after DTC in elderly women, and postoperative monitoring can help prevent and treat OP.