Association Between Vitamin D, Zinc, and Thyroid Biomarker Levels With Vitiligo Disease: A Retrospective Cohort Study in a Tertiary Care Center

Objectives Vitiligo is a dermatological autoimmune disease that has been linked with numerous risk factors. There is an elevated level of evidence suggesting a linkage between vitiligo disease and zinc, vitamin D (Vit-D), thyroid hormones, and thyroid antibody levels. Methods This retrospective cohort study included patients of all age groups of both sexes. Patients were investigated for demographics, vitiligo characteristics, and laboratory tests, including zinc, Vit-D, T3 (triiodothyronine), T4 (thyroxine), thyroid-stimulating hormone (TSH), thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TGAb). Results Two hundred and ninety-seven patients were retrospectively assessed; they averaged 29 years for segmental vitiligo (SV) and 31 years for nonsegmental vitiligo (NSV). Gender-wise, our study included more females (57.5%) than males (42.5%). Females comprised approximately 51.8% of NSV patients, while males constituted 36.7%. Patients' T3, T4, and TPOAb levels correlated significantly with age (p=0.001, p <0.01, p=0.14), and elevated BMI recorded high TPOAb levels (p<0.001). An increase in TGAb was associated with extensive involvement in the depigmentation of body surface area (BSA). The segmental type had the lowest TGAb and TPOAb titers. The universal subtype of vitiligo recorded the highest TSH, T3, and TGAb levels. However, differences in laboratory test levels were insignificant for the sex, the type of vitiligo, or the subtype of vitiligo. Conclusion In conclusion, neither Vit-D nor zinc had a significant linkage with any of vitiligo's characteristics or treatments. Nonetheless, TGAb had a significant correlation to the BSA involved with vitiligo while T4 and TPOAb had a significant association with age, BMI, and BSA overall. Statistically, T3 was linked with age and BSA overall only. More studies with a higher level of evidence are required to establish the association of Vit-D, zinc, thyroid biomarkers, and thyroid antibodies.


Introduction
Vitiligo is an autoimmune disease that causes depigmentation of the skin [1]. It can be classified into two major types, segmental (SV) and nonsegmental vitiligo (NSV) [1,2]. Vitamin D (Vit-D) levels have been linked with the development of numerous autoimmune diseases, such as vitiligo, which might contribute to the role of Vit-D in the regulation of both the adaptive and innate immune systems [3,4]. Zinc is also related to the depigmentation process since melanin has a high affinity for metal ions including zinc. Melanosomes are considered storage for metals, and the loss of pigments, theoretically, can increase zinc levels [5]. Thyroid disturbances in biomarkers, i.e., Triiodothyronine (T3), thyroxine (T4), thyroid stimulating hormone (TSH), thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TGAb), zinc, and Vit-D have been associated with various dermatological manifestations. In addition, Graves' disease and Hashimoto's disease have been correlated with vitiligo, as individuals are more prone to thyroid disturbance [6].
The prevalence of vitiligo worldwide has been investigated in a systematic review with a prevalence of 1.8%. 1 1 1 1 1 Additionally, females have a higher prevalence than males [7]. In a study conducted in Makkah, Saudi Arabia, an incidence of 0.43% was established. Moreover, females were the majority (67.4%), with a female-male ratio of 2.06:1 [8]. Higher Vit-D levels were also correlated with a higher repigmentation rate, and patients are more likely to have a stable form of vitiligo [9]. Zinc is another factor that plays a role in the depigmentation process, which is explained in a study that compared the corticosteroid group versus the zinc sulfate-corticosteroid that manifested responses of 21.43% and 24.7%, respectively [10]. Hashimoto thyroiditis is another autoimmune disease that is associated with vitiligo, which can be attributed to antigen crossover and an increased oxidative stress level [11]. Additionally, TPOAb levels that are associated with Hashimoto disease were significantly higher in vitiligo patients versus the control group (18.1% versus 7.3%, respectively) [12].
Even though previous studies have shown correlations between Vit-D, zinc, TSH levels, and vitiligo, the number of studies that were conducted previously and addressed this topic have substantial limitations, including low levels of evidence, small samples, and insufficient variables [7][8][9][10][11][12]. This study aims to observe and assess possible associations between numerous variables, such as Vit-D, zinc, and thyroid abnormalities, with vitiligo patients in National Guard Health Affairs (NGHA), Saudi Arabia.

Materials And Methods
A retrospective cohort review of medical records encompassed 297 vitiligo patients who visited dermatology clinics within Saudi Arabian National Guard facilities in the western region of Jeddah, Saudi Arabia, from January 2016 to August 2021. Only patients who had their last hospital visit to the dermatology or family medicine department were included according to their diagnosis of vitiligo through the ICD-10 coding system (L80). Simple random sampling was then used to collect their corresponding file numbers, which were distributed to the data collectors. Data were collected by the coauthors utilizing a unified data collection form. Data collection started in August 2021 and was finalized in December 2021. Patients' files were assessed for multiple variables that were divided according to their nature, either quantitative or qualitative as follows.
Quantitative variables included age, body mass index (BMI) body surface area (BSA overall) of patients, BSA affected with depigmentation (BSA involved with vitiligo), T3, T4, TSH, zinc, Vit-D, TPOAb, and TGAb. All labs were assessed with the latest available test results. Qualitative variables included sex, and vitiligo types were divided into segmental, nonsegmental, or unclassified, and subtypes were classified as generalized, acral, acrofacial, focal, mucosal, or universal. The latest topical modality of treatment was evaluated with the use of monobenzone, calcineurin inhibitors, corticosteroids, or other modalities of therapy.
Data were extracted from the collection form and entered into a Microsoft Excel spreadsheet for the aggregation of data. Eventually, the data were exported to SPSS V.26.0 (IBM Inc., Armonk, NY) for data analysis.
Descriptive statistics were calculated for all applicable variables and are presented as mean ± standard deviation or percentage, while the median was calculated for variables with extreme outliers. Kruskal-Wallis test, one-way analysis of variance (ANOVA), and independent t-test analysis were utilized for quantitativequalitative data analysis for all data hypothesizing the data to be normally or abnormally distributed. Chisquare and other variants, i.e., Fisher's exact test, were used for qualitative-qualitative variable analysis. The correlation of quantitative-quantitative data was evaluated using Pearson's correlation coefficient. A Pvalue < 0.05 was considered significant. King Abdullah International Medical Research Centre, National Guard Health Affairs (NGHA), Jeddah, Saudi Arabia granted ethical and research council approval (reference number: JED-21-427780-115144). The research was performed in accordance with The Code of Ethics of the World Medical Association (Declaration of Helsinki).

Results
The mean age of patients with SV was 29 years, while the NSV group's mean age was 31 years. None of the demographic associations were insignificant. However, NSV in female participants was higher than that in male participants (51.8% versus 36.7%). Additionally, the NSV group showed a higher mean BMI and BSA over SV patients. Most participants were single, unlike those with an unclassified diagnosis, which demonstrates a higher married percentage of participants.   Vit-D median levels were higher in males (36.8 nmol/L) than in females (33.1 nmol/L). Additionally, lower TSH mean levels were observed in male patients than in female patients (2.86 ± 4.43 mIU/L versus 3.16 ± 7.66 mIU/L). In contrast, zinc mean levels were elevated in male patients more than in females (17.35 ± 8.19 mmol/L versus 9.89 ±2.27 mmol/L). The median T4 in males was higher than that in females (13.22 mIU/L versus 12.79 mIU/L). In contrast to T4, TPOAb was more elevated in female participants (3.02 IU/m) than in male participants (1.78 IU/m). None of these relations is shown to be significant.   Eight patients were using corticosteroids while 37 were prescribed calcineurin inhibitors as monotherapy.
One hundred fifty-eight used a combination of both. Sixty-nine patients were prescribed monobenzone depigmentation therapy of 25 patients were treated with other modalities of treatment. No association was found in means of TGAb and TPOAb among different modalities of treatment. Monobenzone as a modality of treatment is associated with the highest mean levels of both TGAb and TPOAb, followed by combination therapy. Moreover, calcineurin inhibitors are the third in terms of mean levels of TPOAb. Additionally, corticosteroids demonstrate the lowest mean levels of both TGAb and TPOAb. Though the comparison was insignificant, it is sufficiently high to raise questions regarding its association. Figure 1 compares the latest topical treatment modality and thyroid biomarkers' levels.

FIGURE 1: Thyroid antibodies' levels in different topical modalities of treatment
TPOAb: thyroid peroxidase antibody, TGAb: thyroglobulin antibody No significance was found in this figure

Discussion
Vitiligo is an acquired pigmentary disorder characterized by circumscribed depigmented areas of skin and mucous membranes. It frequently appears in childhood or early adulthood. This disease has an enormous cosmetic impact along with a significant psychological impact [13,14]. In addition, a variegated form of vitiligo is classified into two types: SV and NSV. NSV is classified according to the pattern of involvement: focal, mucosal, generalized, acrofacial, acral, and universal [14][15][16]. The study aims to observe the association of numerous factors, such as Vit-D, zinc, and thyroid abnormalities, with vitiligo patients in the National Guard Health Affairs (NGHA) in Jeddah, Saudi Arabia.
The results showed that the sample with NSV have a higher BMI than those with SV (25.65 ± 7.26 compared to 22.54 ± 8.16). Moreover, the analysis confirmed that the SV group had a lower BSA than NSV participants (1.59 ± 0.43 in comparison with 1.65 ± 0.36). In addition, the data suggest that the NSV cohort tends to be older than SV patients (31 ± 17 compared to 29 ± 17). In terms of sex, the study demonstrated that the percentage of NSV in females was elevated to that in males (51.8% versus 36.7%). Very low correlations were noticed between TSH level and age, BMI, and BSA overall, and no significant associations were established.
Moreover, Moghaddam et al reported lower zinc levels in subjects with vitiligo [13]. Mirnezami and Rahimi also reported low serum zinc levels in generalized patients with vitiligo [14]. female. Moreover, a published article conducted in Riyadh, Saudi Arabia, involving 150 vitiligo patients reflected a percentage of up to 60% of males [3,16].
This article is subject to a small number of limitations. One of which is the fact that it was based on data from a single hospital center in Jeddah, Saudi Arabia, and could not include all participants with vitiligo in the general population. The main disadvantage is that our report was restricted to subjects of National Guard Health Affairs and may not represent all vitiligo patients who are treated in other public hospitals in Saudi Arabia, which shows a lack of diversity regarding ethnicity and socioeconomic status among the included patients. Another drawback is that only the latest available laboratory results were used, and some of these tests were not recently ordered. The absence of a control group is also a large pitfall. Lastly, T3 and zinc levels were not as available in other laboratory tests, which made it difficult to calculate their corresponding means and standard deviations; thus, establishing conclusions was not applicable. Despite these weaknesses, the strengths of our paper outweigh its limitations. This is the first study performed in Saudi Arabia regarding the association between Vit-D, zinc, and thyroid abnormalities with vitiligo. As a result of our findings, we advise frequent screening of thyroid function, anti-thyroid antibodies, and Vit-D levels for patients with vitiligo as recommended by the British Association of Dermatologists guidelines for the management of vitiligo. For future research, we recommend considering prospective studies with larger sample sizes involving the public to obtain optimal findings regarding this topic. In addition, we recommend involving a control group, patients with recent laboratory tests, and including more patients with available T3 and zinc tests to inspect their association with vitiligo.