AUTHOR=Xiao Liu , Zhang Wenjie , Zhu Hongmei , Wang Yueqi , Liu Bin , Huang Rui , Li Lin 

TITLE=Parathyroid Changes After RAI in Patients With Differentiated Thyroid Carcinoma

JOURNAL=Frontiers in Endocrinology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2021.671787

DOI=10.3389/fendo.2021.671787

ISSN=1664-2392

ABSTRACT=<sec><title>Objective</title><p>The purpose of this study was to investigate parathyroid hormone (PTH), serum calcium, phosphorus, and 25-hydroxyvitamin D (25-OH-VD) changes before and after radioactive iodine (RAI) in differentiated thyroid carcinoma (DTC) patients at different time points.</p></sec><sec><title>Methods</title><p>A total of 259 DTC patients who received RAI were prospectively enrolled. We evaluated PTH, serum calcium, phosphorus, and 25-OH-VD levels at baseline pre-RAI, five days, six weeks, and six months post-RAI, respectively. We analyzed the risk factors of hypocalcemia at five days post-RAI.</p></sec><sec><title>Results</title><p>The mean PTH, serum calcium and phosphorus values decreased five days post-RAI compared with pre-RAI (PTH 4.18 ± 1.23 pmol/L <italic>vs</italic>. 3.95 ± 1.41 pmol/L; calcium 2.27 ± 0.09 mmol/L <italic>vs</italic>. 2.20 ± 0.11 mmol/L; phosphorus 1.25 ± 0.17 <italic>vs</italic>. 0.98 ± 0.20 mmol/L, P &lt; 0.05), and the differences were statistically significant. The mean 25-OH-VD levels did not significantly decrease at five days post-RAI. 21.2% (55/259) of patients had hypocalcemia at five days post-RAI, and all of them were given oral calcium supplements. At six weeks post-RAI, all of the above parameters were higher than those at five days post-RAI. Multivariate regression analysis showed that baseline pre-RAI serum calcium &lt; 2.27 mmol/L, PTH &lt; 4.18 pmol/L and negative <sup>99m</sup>TcO<sub>4</sub><sup>-</sup> thyroid imaging were risk factors for hypocalcemia at five days post-RAI.</p></sec><sec><title>Conclusion</title><p>For DTC patients with normal PTH and serum calcium levels at pre-RAI, their PTH, serum calcium, and phosphorus levels decreased at five days post-RAI. About one-fifth of patients could have hypocalcemia at five days post-RAI. Lower baseline pre-RAI serum calcium and PTH levels and negative <sup>99m</sup>TcO<sub>4</sub><sup>-</sup> thyroid imaging were risk factors for hypocalcemia five days post-RAI.</p></sec>