Alopecia Areata Linked to Autoimmune Thyroid Diseases, Suggests Study
Israel: Researchers have found, in a large-scale study, a significant association between alopecia areata and autoimmune thyroid diseases, highlighting the need for closer monitoring of patients with these conditions. The findings were published online in the Journal der Deutschen Dermatologischen Gesellschaft by Jacob Mashiah, Gray Faculty of Medical & Health Sciences, Tel Aviv University, Tel Aviv, Israel, and colleagues.
Alopecia areata (AA) is a chronic, organ-specific autoimmune disorder characterized by patchy, non-scarring hair loss, primarily affecting children and young adults. Its development is linked to a combination of genetic and environmental factors. Previous studies have suggested that AA often coexists with other autoimmune or inflammatory diseases, including systemic lupus erythematosus, vitiligo, and thyroid-related disorders such as Hashimoto's thyroiditis and Graves’ disease. However, the strength of this association has varied across research, making large-scale population-based data critical for better understanding.
To explore this link, researchers conducted a population-based retrospective case-control study using data from Maccabi Healthcare Services (MHS), Israel’s second-largest health fund, which covers around 26% of the country’s population. The study included all individuals diagnosed with AA between 2005 and 2019 and matched them with healthy controls at a 1:2 ratio based on sex. The primary goal was to determine the prevalence of autoimmune thyroid diseases (AITD), specifically Hashimoto's and Graves’ disease, among AA patients compared to controls. Logistic regression models were applied to calculate odds ratios (OR).
The study revealed the following notable findings:
- The study analyzed 33,401 individuals with alopecia areata and 66,802 controls. Both groups had 56.5% males, and the average age at AA onset was 29.9 years.
- Among the total cohort, 5,843 individuals (5.83%) were diagnosed with autoimmune thyroid diseases (AITD), including 5,165 cases of Hashimoto’s disease and 678 cases of Graves’ disease.
- Hashimoto’s thyroiditis was found in 6.93% of AA patients compared to 4.26% of controls, showing a significant association (OR = 1.67).
- Graves’ disease occurred in 0.93% of AA patients versus 0.55% of controls, also indicating a significant link (OR = 1.68).
- Timing analysis revealed that Hashimoto’s disease preceded AA in 55% of cases, while Graves’ disease appeared earlier in 75% of cases.
- Both conditions were diagnosed within three months of AA onset in 3.5% of patients.
- AA was diagnosed before Hashimoto’s in 41.5% of cases and before Graves’ disease in 24.5% of cases.
These findings align with previous research. For instance, a meta-analysis of 17 studies reported an overall OR of 3.66 for AITD in AA patients, while a systematic review involving over 680,000 AA cases demonstrated a strong association with Hashimoto’s thyroiditis (OR = 4.31). Korean population-based data also supported these trends, particularly in patients with severe AA. Other studies suggest that shared genetic factors and thyroid autoantibodies contribute to this association.
The researchers acknowledged limitations, including the retrospective design and inability to adjust for all potential confounders. Nevertheless, the large-scale study reinforces the significant link between AA and autoimmune thyroid disorders.
"Further investigation is needed to determine whether routine thyroid screening should be implemented for individuals diagnosed with AA," the authors concluded.
Reference:
Wohl, Y., Bentov, A., Rubin, R., MaruanI, A., & Mashiah, J. Risk of autoimmune thyroid diseases in individuals with alopecia areata: A nationwide case-control study. JDDG: Journal der Deutschen Dermatologischen Gesellschaft. https://doi.org/10.1111/ddg.15933
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