There is increasing data regarding the association between vitamin D and COVID-19. This study aimed to reveal the alterations of vitamin D metabolism in the setting of COVID-19. We examined 119 adult COVID-19 inpatients and 44 apparently healthy adult individuals with similar serum 25OH-D₃ levels as a reference group. The assessment included serum biochemical parameters (total calcium, albumin, phosphorus, creatinine), parathyroid hormone (PTH), vitamin D-binding protein (DBP), vitamin D metabolites (25OH-D₃, 25OH-D₂, 1,25(OH)₂D₃, 3-epi-25OH-D₃, 24,25(OH)₂D₃ and D₃) and free 25OH-D. COVID-19 patients had in general very low vitamin D levels (median 25OH-D₃ equals 10.8 ng/mL), accompanied by an increased production of the active vitamin D metabolite (1,25(OH)₂D₃), estimated as higher 1,25(OH)₂D₃ serum levels (61 [44; 81] vs. 40 [35; 50] pg/mL, p < 0.001) and lower 25OH-D₃/1,25(OH)₂D₃ ratio (175 [112; 260] vs. 272 [200; 433], p < 0.001) which is presumably aimed at preventing hypocalcemia. Patients with COVID-19 also had elevated DBP (450 [386; 515] vs. 392 [311; 433] mg/L, p < 0.001) and low free 25OH-D levels (<LoB vs. 3.9 [3.2; 4.4] pg/mL, p < 0.001). Follow-up assessment of the COVID-19 inpatients showed recovery of the observed changes. Overall, hospitalized patients with an acute course of COVID-19 have not only very low levels of 25OH-D but also profound abnormalities in the metabolism of vitamin D regardless of the clinical course of the disease. These alterations might exacerbate existing vitamin D deficiency and its negative impact.

In current clinical practice, a thorough understanding of vitamin D metabolism is in high demand both for patients with various diseases and for healthy individuals. Analytical techniques that provide simultaneous measurement of multiple metabolites are preferred. Herein, the development of an HPLC-DMS-MS/MS method for the quantitation of vitamin D compounds (25(OH)D₃, 25(OH)D₂, 1,25(OH)₂D₃, 3-epi-25(OH)D₃, 24,25(OH)₂D₃, and D₃) in serum is described. The selected sample preparation procedure based on the combination of liquid–liquid and solid-phase extraction, which excluded a lengthy derivatization step, was compared with other common approaches. Sensitivity was increased through the implementation of differential ion mobility separation. The proposed assay allowed us to determine the low abundant 1,25(OH)₂D₃ with the detection limit of 10 pg/mL. The validation study showed good linearity (r² > 0.99), a wide analytical range (2.5–75 ng/mL for 25(OH)D₃), and acceptable precision (<7%) for all metabolites. The recovery ranged from 71% to 93% and the matrix effect from 0.80 to 0.95 depending on the metabolite; accuracy determination was performed using DEQAS controls.

In this prospective controlled study, we examined 25 adults with adequately controlled (HbA1c level < 8.0%) type 1 diabetes mellitus (T1DM) and 49 conditionally healthy adults, intending to reveal the diversity of vitamin D metabolism in the setting of cholecalciferol intake at a therapeutic dose. All patients received a single dose (150,000 IU) of cholecalciferol aqueous solution orally. Laboratory assessments including serum vitamin D metabolites (25(OH)D₃, 25(OH)D₂, 1,25(OH)₂D₃, 3-epi-25(OH)D₃ and 24,25(OH)₂D₃), free 25(OH)D, vitamin D-binding protein (DBP) and parathyroid hormone (PTH) as well as serum and urine biochemical parameters were performed before the intake and on Days 1, 3 and 7 after the administration. The studied groups had no significant differences in baseline parameters except that the patients with diabetes showed higher baseline levels of free 25(OH)D (p < 0.05). They also lacked a correlation between the measured and calculated free 25(OH)D in contrast to the patients from the control group (r = 0.41, p > 0.05 vs. r = 0.88, p < 0.05), possibly due to the glycosylation of binding proteins, which affects the affinity constant for 25(OH)D. The elevation of vitamin D levels after the administration of cholecalciferol was comparable in both groups, with slightly higher 25(OH)D₃ levels observed in the diabetes group throughout the study since Day 1 (p < 0.05). Overall, our data indicate that in patients with adequately controlled T1DM 25(OH)D₃ levels and the therapeutic response to cholecalciferol is similar to that in healthy individuals.

AIM. To study the role of iodine, selenium and zinc in the pathogenesis of iodine deficiency and autoimmune thyroid diseases and scientifically substantiate the choice of security biomarkers and analytical methods for determination.MATERIALS AND METHODS. Serum iodine (I), selenium (Se), and zinc (Zn) concentrations were measured using inductively coupled plasma ionization tandem mass spectrometry (Agilent 8900 ICP-MS Triple Quad); by chemiluminescent immunoassay on an automatic analyzer Architect i2000 — TSH and AT-TPO in blood serum; by enzyme immunoassay — ZnT8A; biochemical method — ALP, SOD1 in 1150 people aged from 18 to 65 years (the average age of the subjects was 40±5 years). Ultrasound of the thyroid gland was performed in the supine position using a portable ultrasound machine LOGIQe with a multifrequency linear sensor 10–15 MHz; during the study, the volume of the thyroid gland, the presence of nodules and their characteristics according to the TIRADS classification, the structure of the thyroid gland and its echogenicity were assessed.RESULTS. In our study, the median serum iodine concentration was 60.68 μg/L (n=1150), with no significant difference between sexes. In 2%, the level of iodine in the blood serum was less than 30 mcg/l. Among the samples obtained (n=57), 19% were found to have a reduced iodine content in the lipophilic fraction — less than 10% of the total. In these samples, additional studies were performed on TSH, total and free T3 and T4 fractions. As a result, all indicators fell within the normal range, which indicates that there was no effect on thyroid function from a decrease in iodine content in the lipophilic fraction. In a comparative analysis of our previously obtained results of determining iodine in urine using the cerium-arsenite method and the inductively coupled plasma mass spectrometry method, it was found that both methods are generally comparable. The median selenium concentration was 83.38 µg/l, which corresponds to the reference values. The proportion of individuals with serum selenium levels less than 40 μg/L was 2.2%. A comparative analysis of groups of patients with serum selenium concentrations of less than 100 µg/l and more than 100 µg/l was carried out; in the group with low-normal selenium levels, the incidence of autoimmune thyroid pathology is 5% higher than in the comparison group. 60.3% of the adult population had zinc levels less than 1000 μg/L. The median serum zinc concentration was 632.9 μg/L. In regions with zinc deficiency, the incidence of autoimmune diseases (AI) of the thyroid gland and nodular / multinodular goiter is on average 10% higher than in regions with optimal zinc supply. There was no relationship between the content of zinc in the blood serum and antibodies to the zinc transporter (ZnT8A), alkaline phosphatase (ALP) and superoxide dismutase (SOD1), including in comparison of the data obtained in carriers of AT-TPO and in the comparison group (among carriers of AT-TPO: the median concentration of zinc was 644.4 μg/l, SOD1 — 117.2 ng/ml, ALP — 70.3 U/l, antibodies to ZnT8A — 249.8; in the comparison group — median zinc concentration — 744.6 μg/l, SOD1 — 102.4 ng/ml, ALP — 66.1 U/l, antibodies to ZnT8A — 242).Thus, based on the data obtained, the relationship between thyroid pathology and micronutrient deficiencies was confirmed. No convincing evidence has been obtained on the study of additional diagnostic markers of Zn deficiency, which casts doubt on the advisability of their determination in routine practice. The ICP-MS method made it possible to propose its own reference values for I, Se, Zn and is comparable to the cerium-arsenite method in sensitivity and specificity when studying I in urine. However, due to technical features and limitations in sample size, the study population requires further improvement.

Background. Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders in women of reproductive age. Recently, the role of melatonin in the pathogenesis of this syndrome became widely discussed among the scientists, because there is an evidence of its impact on the reproductive function and maturation of oocytes.Aim. To study a informativeness of melatonin determination and its relationship with sleep disorders in PCOS.Materials and methods. The study involved 120 women aged 17–35 years: 60 patients with PCOS and 60 women without this disorder as controls. The level of melatonin in the blood, saliva and its metabolite in urine – 6 sulfatoximelatonin were analyzed. To identify sleep disorders survey was conducted using a questionnaire scoring subjective sleep characteristics.Results. Sleep disorders based on subjective scoring profiles sleep characteristics were identified in PCOS group (up to 70% of patients) regardless of BMI. The level of 6-sulfatoximelatonin in urine, nocturnal melatonin levels in saliva (at 3:00 AM) and melatonin in the blood were significantly higher in patients with PCOS compared with the control group regardless of BMI. The level of melatonin in follicular fluid was lower in patients with PCOS. There was a significant correlation of melatonin levels in the blood and the degree of sleep disorders according to the questionnaire scoring subjective sleep characteristics, the level of melatonin in saliva at 3:00 AM and a 6-sulfatoximelatonin in daily urine (p = 0.046).Conclusions. PCOS is polyetiology disease, and an important role in the formation and progression in which plays melatonin. Correlation of levels of this hormone in different body fluids suggests its systemic action and direct involvement in the regulation of reproductive function.

A new quantification method is proposed for the determination of serum estrone (E1), estradiol (E2), and estriol (E3) based on high-performance liquid chromatography–tandem mass spectrometry combined with differential ion mobility separation (SelexION Technology). This approach allows determining analytes with limits of detection of 4.5, 18 and 45 fg on column for E1, E2, and E3, respectively. The lowest limits of quantification are 0.1, 0.5, and 0.5 pg mL^–1 in serum for E1, E2, and E3, respectively. The suitability of proposed method for diagnostic purposes is demonstrated in an analysis of serum from 114 patients of different genders and ages.