Impact of Thyroid Dysfunction on Hair Disorders

Thyroid Dysfunction and Alopecia Areata: A Genetic Prediction Causality Analysis Study

BACKGROUND

Observational studies have suggested a correlation between alopecia areata (AA) and thyroid dysfunction (TD). However, the causal relationship between AA and TD remains uncertain. The purpose of this study is to investigate the causal relationship between these two conditions. Understanding the potential causal relationship between AA and TD is valuable for elucidating the pathogenesis of AA and for designing innovative methods to prevent and treat AA and its related complications.

METHODS

All data for this two-sample Mendelian randomization (MR) study were sourced from public databases. This study selected hypothyroidism, Hashimoto's thyroiditis, hyperthyroidism, subacute thyroiditis, and Graves' disease as exposure factors, with AA as the outcome variable. Data for hypothyroidism, Hashimoto's thyroiditis, hyperthyroidism, subacute thyroiditis, Graves' disease, and AA were obtained from related genome-wide association studies (GWAS). Various MR analysis methods such as inverse variance weighted (IVW), MR-Egger, and weighted median were utilized. Additionally, Cochrane's Q test was used to detect heterogeneity in MR results, and the MR-Egger intercept test and MR pleiotropy residual sum and outlier (MR-PRESSO) test were used to detect horizontal pleiotropy. A leave-one-out analysis was conducted to investigate the sensitivity of this association.

RESULTS

We found statistically significant genetic predictions of AA with hypothyroidism, Hashimoto's thyroiditis, and subacute thyroiditis (IVW OR = 1.4009815, 95% confidence interval [CI]: 1.1210399-1.750829; p = 0.003030698, OR = 1.396101, 95% CI: 1.030134-1.89208; p = 0.03144273, OR = 0.732702, 95% CI: 0.604812-0.887634; p = 0.001483368). Furthermore, tests for pleiotropy showed no evidence of pleiotropy, enhancing the credibility of the study results. Finally, the leave-one-out test demonstrated the stability and robustness of this association.

CONCLUSION

This study provides new evidence of a potential genetic link between thyroid issues and AA. By employing the two-sample MR method to eliminate confounding factors and reverse causation, unbiased results were obtained, confirming a causal relationship between hypothyroidism, Hashimoto's thyroiditis, subacute thyroiditis, and AA. This lays the foundation for further mechanistic studies and potential clinical applications. Future research should further explore the specific biological mechanisms between TD and the onset of AA.

The genetic link between thyroid dysfunction and alopecia areata: a bidirectional two-sample Mendelian randomization study

Background

Although descriptive studies have found an association between thyroid dysfunction (TD) and alopecia areata (AA), however, the causal relationship between TD and AA remains unclear. The purpose of this study is to investigate the causal relationship between the two and the specific directions.

Methods

We performed large-scale, two-sample Mendelian randomization (MR) analyses to examine whether there was an association between TD (such as Graves' disease (GD), Hashimoto's thyroiditis (HT), thyroid cancer (TC), thyroid stimulating hormone (TSH), thyrotropin-releasing hormone (TRH), etc.) and AA. Genome-wide association study (GWAS) summary statistics for TD and AA were from the IEU OpenGwas project. The inverse variance-weighted (IVW) method was used as the primary analysis method to evaluate the causality between TD and AA, supplemented by the weighted median, MR-Egger, simple mode and weighted mode. In addition, sensitivity analyses were performed to assess the reliability of the study results.

Results

Our study found that single nucleotide polymorphisms (SNPs) in HT (IVW OR = 1.396, 95% CI 1.030-1.892, P=0.031) and hypothyroidism (IVW OR = 1.431, 95% CI 1.138-1.799, P=0.002) significantly increased the risk of AA. Reverse MR analysis indicated that genetic susceptibility to AA (β=-0.029, 95%CI=-0.051 to -0.007, P=0.009) may be a risk for TRH. Positive MR analysis observed no statistically significant causal relationship between other TD and AA (IVW P>0.05). Reverse MR analysis also showed no statistically significant association between AA and other TD (IVW P>0.05) other than TRH. Furthermore, additional sensitivity analyses were performed, including a leave-one-out test, a heterogeneity test, and a pleiotropy test to assess the robustness of the results.

Conclusions

This study provides a very comprehensive analysis of the causal relationship between TD and AA, providing convincing genetic evidence to support the causal relationship between TD and alopecia areata. It reveals some causes of AA patients, which is of great significance for the management and treatment of AA patients.

Is thyroid dysfunction a common cause of telogen effluvium?: A retrospective study

Telogen effluvium (TE) is a common cause of hair loss characterized by excessive resting hair shedding. Thyroid dysfunction is one of the possible causes of TE. On the other hand, the link between thyroid disorder and TE is still being debated. The aim of this retrospective is to investigate the link between thyroid dysfunction and TE. This retrospective study included 500 female patients with TE who had thyroid function testing between January 2012 and December 2022. Patients were eligible if they had a confirmed TE diagnosis and thyroid function tests within 3 months of being diagnosed with TE. The thyroid function of the participants was classified as euthyroid, hypothyroidism, or hyperthyroidism. The severity of hair loss was determined using the severity of alopecia tool (SALT) score. The study included 500 TE females, 248 of whom were euthyroid, 150 had hypothyroidism, and 102 had hyperthyroidism. The hypothyroid group had a significantly higher mean SALT score than the other 2 groups. Furthermore, patients in the hypothyroid group had a higher proportion of severe hair loss. The mean SALT score did not differ significantly between groups with normal thyroid function and those with hyperthyroidism. A common cause of TE is thyroid dysfunction, particularly hypothyroidism. Patients with hypothyroidism have more severe hair loss than those with normal thyroid function or hyperthyroidism. To effectively identify and manage such cases, thyroid function testing should be included in the diagnostic workup of patients with TE.