Abstract: Objective To explore the dynamic variation rule of serum calcium levels,serum parathyroid hormone levels and central drainage fluid parathyroid hormone levels after total thyroidectomy,To investigate the clinical significance of monitoring the above indexes in evaluating parathyroid function.Methods From January 2018 to January 2021,112 patients who received total thyroidectomy and bilateral central lymph node dissection in general Surgery Department of Qinghai provincial People's Hospital were chosen as the research objectve,According to the number of parathyroid glands(0, 1, 2) retained in situ,patients were divided into group A0,group A1 and group A2,Serum calcium,blood PTH and central drainage fluid PTH levels were detected before surgery and 1 to 4 days after surgery,Then we did a statistical analysis.Results There were 23 cases of hypocalcemia in 112 patients,including 15 cases in group A0,6 cases in group A1 and 2 cases in group A2.The level of postoperative serum calcium were lower than those before operative,And the most obvious decrease was  group A0,There was no significant increase in postoperative 1～4 days,However,group A1 and A2 showed a trend of gradual increase,and group A2 showed a faster increase.The level of postoperative serum PTH were lower than those before operative,And the most obvious decrease was group A0,There was no significant increase in postoperative 1～4 days,The level of serum PTH in group A1 and group A2 showed an upward trend,But the level of serum PTH in the two groups did not increase to the preoperative level within 4 days after operation.The level of postoperative drainage fluid PTH was significantly different among all groups,With group A2 having the highest mean value,Group A1 followed by group A0 having the lowest.With the passage of time,there was no significant change in group A0,And the PTH level of drainage fluid in group A1 and group A2 showed a general downward trend,As well,The decrease of group 1 was faster than that of group A2.Conclusion By monitoring serum calcium,serum PTH and drainage fluid PTH,the functional recovery of orthotopic parathyroid gland can be effectively evaluated after thyroidectomy,The central drainage fluid PTH can directly reflect the activity of the in-situ retained parathyroid gland,The maintenance of a high level of postoperative drainage is direct evidence of orthotopic parathyroid survival.

Key words: thyroidectomy, serum parathyroid hormone, serum calcium, parathyroid function, central drainage fluid parathyroid hormone