Wide Spectrum of Thyroid Function Tests in COVID-19: From Nonthyroidal Illness to Isolated Hyperthyroxinemia

Background: Changes in thyroid function test (TFT) in COVID-19 patients have been reported in several studies. However, some features such as thyrotoxicosis are inconsistent in these studies. In addition, some drugs such as heparin interfere with the free T4 assay. Objectives: This study was designed to examine TFT abnormalities in COVID-19, utilizing direct and indirect methods of free T4 assay. Methods: This prospective cross-sectional study was conducted on 131 hospitalized COVID-19 patients. Serum levels of total T3, TSH, T3RU, and total T4 were measured. The free T4 assay was performed using direct (free T4) and indirect (free thyroxin index or FT4I) methods. The patients were categorized into different TFT groups. The clinical characteristics, laboratory findings, and outcomes were compared between the groups. Results: The frequencies of Nonthyroidal Illness (NTI), subclinical/overt hypothyroidism and subclinical/overt thyrotoxicosis were 51.7, 6.9, and 6.9%, respectively. Besides, 6 and 8.1% of the patients had isolated high free T4 and isolated high FT4I without any other TFT abnormality, respectively. The lymphocyte percent was lower in the subclinical/overt group than in other TFT groups (P = 0.002). Atrial Fibrillation (AF) was found in 37.5% of subclinical/overt thyrotoxicosis patients versus 1.7% in the NTI and nil in the other three groups (P < 0.001). Conclusions: In addition to the reported TFT abnormalities in COVID-19 in previous studies, some new features like isolated hyperthyroxinemia were found in our study. We found a strong association between subclinical/overt thyrotoxicosis and AF. Regarding the high prevalence of AF in hospitalized COVID-19 patients, the thyroid function test is rational in COVID-19 patients with this arrhythmia

Contributing Factors for Calcium Changes During Hospitalization in COVID-19: A Longitudinal Study

Abstract Background: Hypocalcemia is highly prevalent in Coronavirus disease 2019 (COVID-19). There is limited evidence about the course and roles of different parameters in the occurrence of new or worsening hypocalcemia. Objectives: This prospective longitudinal study was conducted on hospitalized COVID-19 patients in Qazvin, Iran, in 2021. Methods: Serum levels of calcium, albumin, parathormone (PTH), 25(OH)D (vitamin D), magnesium, and phosphate were assessed on the first day (time one), as well as fourth to sixth days (time two) of hospitalization. Paired t-test, McNemar’s test, and multivariate logistic regression test were used to compare data at two times and evaluating the independent roles of different variables in the occurrence or worsening of hypocalcemia. Results: Out of a total of 123 participants, 102 patients completed the study. The mean serum calcium level significantly decreased from 8.32 ± 0.52 mg/dL to 8.02 ± 0.55 mg/dL at time two compared to time one (P < 0.001). Also, we witnessed new or worsening hypocalcemia at time two in 44 (55%) patients with normal serum calcium or mild hypocalcemia at time one (P < 0.001). The PTH level decreased from 42.17±27.20 pg/mL to 31.28±23.42 pg/mL (P < 0.001). The decrease in albumin and PTH levels was an independent significant factor in the occurrence or worsening of hypocalcemia at time two (OR = 1.27; 95% CI: 1.10 - 1.46; P = 0.001 for each 1 g/L decrement albumin and OR = 1.29; 95% CI: 1.03 - 1.62; P = 0.026 for each 10 pg/mL decrement PTH). Vitamin D deficiency or changes during hospitalization did not have a significant role in new or worsening hypocalcemia. Conclusions: Decreased PTH secretion and hypoalbuminemia have significant roles in the occurrence of new or worsening hypocalcemia during hospitalization due to COVID-19. Keywords: Hypocalcemia, COVID-19, Parathormone, Vitamin

Hypocalcemia in hospitalized patients with COVID‑19: roles of hypovitaminosis D and functional hypoparathyroidism

Introduction Despite the high prevalence of hypocalcemia in patients with COVID-19, very limited studies have been designed to evaluate etiologies of this disorder. This study was designed to evaluate the status of serum parameters involved in calcium metabolism in patients with COVID-19 and hypocalcemia. Materials and methods This cross-sectional study was conducted on 123 hospitalized patients with COVID-19. Serum concentrations of PTH, 25 (OH) D, magnesium, phosphate, and albumin were assessed and compared across three groups of moderate/severe hypocalcemia (serum total calcium<8 mg/dl), mild hypocalcemia (8 mg/dl≤serum total calcium<8.5 mg/ dl) and normocalcemia (serum total calcium≥8.5 mg/dl). Multivariate analyses were performed to evaluate the independent roles of serum parameters in hypocalcemia. Results In total, 65.9% of the patients had hypocalcemia. Vitamin D defciency was found in 44.4% and 37.7% of moderate/ severe and mild hypocalcemia cases, respectively, compared to 7.1% in the normal serum total calcium group (P=0.003). In multivariate analysis, vitamin D defciency was independently associated with 6.2 times higher risk of hypocalcemia (P=0.001). Only a minority of patients with hypocalcemia had appropriately high PTH (15.1% and 14.3% in mild and moderate/severe hypocalcemia, respectively). Serum PTH was low/low-normal in 40.0% of patients with moderate/severe low-corrected calcium group. Magnesium defciency was not associated with hypocalcemia in univariate and multivariate analysis. Conclusion Vitamin D defciency plays a major role in hypocalcemia among hospitalized patients with COVID-19. Inappropriately low/low-normal serum PTH may be a contributing factor in this disorder