The Impact of Sunlight Exposure on Postoperative Hypoparathyroidism: A Retrospective Analysis from Two Greek Centers

<b>Background:</b> Postoperative hypoparathyroidism is a common complication of thyroid surgery. Sunlight is a natural source of ultraviolet B (UVB) radiation, which facilitates the synthesis of vitamin D3 in the skin. Inadequate sunlight exposure has been linked to vitamin D deficiency, potentially exacerbating the risk of hypocalcemia in patients undergoing thyroid surgery. The aim of the present study is to evaluate the effect of sunshine levels on postoperative hypoparathyroidism. <b>Method:</b> We retrospectively evaluated patients that underwent total thyroidectomies at two different centers (Thessaloniki and Rhodes) by the same surgical team from 2021 to 2023 in terms of postoperative hypoparathyroidism. We compared the sunshine levels at each center the year before surgery and correlated them with postoperative levels of parathyroid hormone, serum ionized calcium, and phosphorus. <b>Results:</b> One-hundred twenty patients (Group Thessaloniki = 60 patients, Group Rhodes = 60 patients) who were matched for demographic characteristics and type of thyroid disease and surgery were enrolled in our study. The sunshine levels were different between the two centers (Rhodes > Thessaloniki, <i>p</i> < 0.001). It was found that sunshine levels affect preoperative serum ionized calcium (<i>p</i> = 0.002) and postoperative parathyroid hormone levels (<i>p</i> = 0.025). <b>Conclusions:</b> Sunlight exposure levels may play a crucial role in preventing postoperative hypoparathyroidism. Patients living in locations with higher sunshine levels may have lower rates of postoperative hypoparathyroidism.