Endocrine Abstracts

Hypocalcemia has been recently identified as a major biochemical distinctive feature of COVID-19, predicting poor clinical outcomes. Besides the calcium-dependent viral mechanisms of action and the enhanced cellular permeability to calcium ions, we previously hypothesized that hypovitaminosis-D could be a predisposing factor to hypocalcemia. Actually, high prevalence of vitamin D (VD) deficiency in COVID-19 patients (pts) was reported by several studies, but, to date, only few tried to investigate the role of hypovitaminosis-D on calcium and parathyroid hormone (PTH) levels. We aimed at evaluating the relationship between calcium, PTH and VD in COVID-19 pts. Patients admitted to San Raffaele University Hospital for COVID-19 from February 2020 were enrolled in this study. We excluded pts with comorbidities and therapies influencing calcium and VD metabolism. Ionized and total calcium, 25OH-Vitamin D and PTH levels were evaluated at admission in hospital. VD insufficiency and deficiency were defined as VD level below 30 ng/ml and 20 ng/ml, respectively. We defined hypocalcemia for ionized calcium (Ca²⁺) level below 1.18 mmol/l and total calcium (tCa) level below 2.1 mmol/l. Hyperparathyroidism was defined as PTH above 65 pg/ml. A total of 88pts were included in the study. Median (IQR) tCa and Ca²⁺ levels were 2.15 (2.05–2.22) mmol/l and 1.14 (1.11–1.18) mmol/l, respectively. Low total and ionized calcium levels were found in 36.5% and in 72.9% of pts, respectively. Median (IQR) VD levels were 16.3 (11.2–23.9) ng/ml. VD insufficiency and deficiency were observed in 88.6% and in 68.2% of pts, respectively. Median (IQR) PTH levels were 46.2 (37.4–64.5) pg/ml and hyperparathyroidism was detected only in 23.9% of pts. No significant differences were found in serum PTH levels between patients with VD insufficiency vs. sufficiency (46.5 (38.2–65.3) vs. 41 (27.5–63.4) pg/ml) and between hypocalcemic vs. normocalcemic pts (Ca²⁺ 49.5 [37.7–65.7] pg/ml vs. 48.5 [37.2–56.6] pg/ml; P = 0.15). Linear regression analyses showed a positive correlation between VD and tCa (P = 0.017; r = 0.26). A borderline significant negative correlation between VD and PTH (P = 0.049; r =–0.21) was also detected. Finally, PTH negatively correlated with Ca²⁺ levels (P < 0.001; r =–0.35). In conclusion, we confirmed a high prevalence of hypocalcemia in COVID-19 pts and showed for the first time that it occurred largely in the context of marked hypovitaminosis-D not adequately compensated by secondary hyperparathyroidism, the reasons of which need to be explored. Since hypocalcemia may be marker and cause of severe clinical consequences in COVID-19, we can hypothesize that VD supplementation may play a relevant role in COVID-19, also possibly preventing hypocalcemia.