A mechanistic linkage between oral lichen planus and autoimmune thyroid disease

Thyroid Dysfunction and Oral Lichen Planus: Evidence From Two-Sample Mendelian Randomization Analysis

INTRODUCTION AND AIMS

Epidemiological studies have shown that the association between thyroid dysfunction (TD) and oral lichen planus (OLP) is controversial, and the causal relationship remains ill-defined. This study aims to investigate their probable mutual causality using bidirectional Mendelian randomization (MR) analyses.

METHODS

We extracted genetic instruments for OLP and 10 phenotypes of TD from the genome-wide association studies database. The inverse variance weighted method was primarily used to evaluate the bidirectional causal relationship between TD and OLP. The results' robustness was verified by sensitivity analysis (Cochran's Q test, MR-Egger intercept, and leave-one-out test). Bonferroni correction threshold (0.05/10) was applied to determine significant differences.

RESULTS

Forward MR analysis indicated that Hashimoto's thyroiditis (HT) was suggestively linked to a higher likelihood of developing OLP (P = .0077), while hypothyroidism significantly increased the risk of OLP occurrence (P = .0002). The reverse MR study found that OLP was suggestively related to the occurrence of hyperthyroidism (P = .0126) and thyroid cancer (P = .0244). Furthermore, OLP was found to significantly increase the risk of HT (P = 3.47 × 10-⁸), Graves' disease (P = 1.03 × 10-⁵), hypothyroidism (P = 1.08 × 10-⁸), and elevated thyroid-stimulating hormone levels (P = 1.99 × 10-⁶). No major pleiotropy or heterogeneity was detected (P > .05).

CONCLUSION

These findings suggest that hypothyroidism significantly increases the risk of OLP, while OLP may contribute to the development of autoimmune thyroid disorders, particularly HT, Graves' disease, hypothyroidism, and thyroid-stimulating hormone. These findings highlight the complex interaction between endocrine and immune systems, emphasizing the need for further research into shared molecular pathways and potential clinical implications.

CLINICAL RELEVANCE

This study provides a genetic foundation for understanding the relationship between TD and OLP, which aids early screening and diagnosis and informs therapy development.

Association Between Oral Lichen Planus and Thyroid Disease: A Cross-Sectional Study

Background: In recent years, various authors have suggested a potential association between oral lichen planus (OLP) and thyroid disease (TD), although other studies have failed to confirm a significant relationship. The available literature presents inconsistent and sometimes contradictory findings. Additionally, other conditions-such as anxiety and depression, hypertension, diabetes mellitus, and dyslipidemia-have also been linked with OLP. Methods: A cross-sectional study was conducted involving 120 participants, comprising 60 patients diagnosed with OLP and 60 controls. Medical histories related to TD and other comorbidities were collected for both groups. Results: The prevalence of TD among the OLP patients was 20%, compared to 6.7% in the control group. The most frequently observed thyroid disorder was hypothyroidism, identified in 13.3% of the patients with OLP. Statistically, there was a moderate probability of an association between OLP and TD (p = 0.054). No statistically significant associations were found between OLP and hypertension (p = 0.378), type 2 diabetes mellitus (p = 0.550), dyslipidemia (p = 0.562), anxiety (p = 0.959), or depression (p = 0.532). Conclusions: Although the association between OLP and TD remains inconclusive, our findings suggest a moderate statistical probability of a relationship.

Laboratory investigation of the association between oral lichen planus and Hashimoto's thyroiditis

BACKGROUND

Previous studies have shown some relationship between oral lichen planus (OLP) and certain systemic comorbidities. The aim of this study was to investigate laboratory parameters between cases of Hashimoto's thyroiditis (HT) concomitant with OLP and cases of HT only.

METHODS

This case-control study comprised 59 HT patients with OLP and 76 without OLP, all of whom had 5 serum thyroid-related indicators, including thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TGAb), thyroid stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4).

RESULTS

Compared to cases of HT only, female predominance, presence of thyroid nodules, positive TGAb, and higher FT3/FT4 ratio were mainly observed in cases of HT concomitant with OLP (all P < 0.05). Multivariate regression analysis revealed that presence of thyroid nodules (odds ratio [OR], 10.328; 95% confidence interval [CI], 2.564-41.604), positive TGAb (OR, 6.936; 95%CI, 2.024-23.765), and higher FT3/FT4 ratio (OR, 2.577; 95%CI, 1.377-4.823) were associated significantly (all P < 0.005) with higher risk of OLP occurrence in 135 HT patients. Notably, these significant associations were not found among 30 male patients but did among 105 female patients in regression analysis.

CONCLUSION

This retrospective study revealed that presence of thyroid nodule, positive TGAb, and high FT3/FT4 ratio as risk factors were significantly associated with OLP occurrence risk in female patients with HT. This suggests that female patients suffering from HT, particularly who presented with the risk factors, should be informed about the risk of OLP development and the need for oral mucosal examination to screen for lichen lesions.

Familial oral lichen planus: A new risk group for oral cancer?

OBJECTIVE

The familial type of oral lichen planus (OLP) is rare, with a paucity of data regarding its clinical significance. Our objective was to characterize patients with familial OLP.

METHODS

Families with at least two members diagnosed with OLP were included. Clinical and demographic data and medical history were recorded.

RESULTS

Twenty families, 19 Jewish and 1 Arab, were identified. Of the Jewish families, 57.8% were non-Ashkenazi, originating mainly from central Asia. Of those with OLP there were 14 males and 23 females with an average age of 49.1. Dyslipidemia, cardiovascular, and thyroid disorders (27.7%, 22.2%, and 16.6%, respectively) were the most common comorbidities. Five patients from five distinct families had oral cancer, two with second primary.

CONCLUSIONS

To the best of our knowledge, this is the largest study describing familial OLP. The predominant and common ethnicity of the families with multiple members diagnosed with OLP may imply an ethnic tendency. The higher tendency of hypothyroidism and the high percentage of OSCC among familial OLP patients might be connected to familial OLP and the latter suggests that this population is predisposed to malignant transformation. Thus, this group should be considered as a high-risk group.

Crossroads between Skin and Endocrine Glands: The Interplay of Lichen Planus with Thyroid Anomalies

In this narrative review, we aimed to overview the interplay between lichen planus (LP) and thyroid conditions (TCs) from a dual perspective (dermatologic and endocrine), since a current gap in understanding LP-TC connections is found so far and the topic is still a matter of debate. We searched PubMed from Inception to October 2023 by using the key terms "lichen planus" and "thyroid", (alternatively, "endocrine" or "hormone"). We included original clinical studies in humans according to three sections: LP and TC in terms of dysfunction, autoimmunity, and neoplasia. Six studies confirmed an association between the thyroid dysfunction (exclusively hypothyroidism) and LP/OL (oral LP); of note, only one study addressed cutaneous LP. The sample size of LP/OLP groups varied from 12-14 to 1500 individuals. Hypothyroidism prevalence in OLP was of 30-50%. A higher rate of levothyroxine replacement was identified among OLP patients, at 10% versus 2.5% in controls. The highest OR (odd ratio) of treated hypothyroidism amid OLP was of 2.99 (p < 0.005). Hypothyroidism was confirmed to be associated with a milder OLP phenotype in two studies. A single cohort revealed a similar prevalence of hypothyroidism in LP versus non-LP. Non-confirmatory studies (only on OLP, not cutaneous LP) included five cohorts: a similar prevalence of hypothyroidism among OLP versus controls, and a single cohort showed that the subjects with OLP actually had a lower prevalence of hypothyroidism versus controls (1% versus 4%). Positive autoimmunity in LP/OLP was confirmed in eight studies; the size of the cohorts varied, for instance, with 619 persons with LP and with 76, 92, 105, 108, 192, 247, and 585 patients (a total of 1405) with OLP, respectively; notably, the largest control group was of 10,441 individuals. Four clusters of approaches with respect to the autoimmunity in LP/OLP were found: an analysis of HT/ATD (Hashimoto's thyroiditis/autoimmune thyroid diseases) prevalence; considerations over the specific antibody levels; sex-related features since females are more prone to autoimmunity; and associations (if any) with the clinical aspects of LP/OLP. HT prevalence in OLP versus controls was statistically significantly higher, as follows: 19% versus 5%; 12% versus 6%; and 20% versus 9.8%. A single study addressing LP found a 12% rate of ATDs. One study did not confirm a correlation between OLP-associated clinical elements (and OLP severity) and antibody values against the thyroid, and another showed that positive TPOAb (anti-thyroperoxidase antibodies) was more often found in erosive than non-erosive OLP (68% versus 33%). Just the reverse, one cohort found that OLP subjects had a statistically significantly lower rate of positive TPOAb versus controls (9% versus 15%). Five case-control studies addressed the issue of levothyroxine replacement for prior hypothyroidism in patients that were diagnosed with OLP (no study on LP was identified); three of them confirmed a higher rate of this treatment in OLP (at 8.9%, 9.7%, and 10.6%) versus controls. In conclusion, with regard to LP/OLP-TC, we note several main aspects as practical points for multidisciplinary practitioners: OLP rather than LP requires thyroid awareness; when it comes to the type of thyroid dysfunction, mostly, hypothyroidism should be expected; female patients are more prone to be associated with ATDs; a potential higher ratio of OLP subjects taking levothyroxine was found, thus a good collaboration with an endocrinology team is mandatory; and so far, OLP individuals have not been confirmed to be associated with a higher risk of thyroid nodules/cancer.

The Hypothalamic-Pituitary-Thyroid Axis Equivalent in Normal and Cancerous Oral Tissues: A Scoping Review

The hypothalamic-pituitary-thyroid (HPT) axis is crucial in regulating thyroid hormone levels that contribute to the development and homeostasis of the human body. Current literature supports the presence of a local HPT axis equivalent within keratinocytes of the skin, with thyroid hormones playing a potential role in cancer progression. However, this remains to be seen within oral tissue cells. An electronic search of Scopus and PubMed/Medline databases was conducted to identify all original publications that reported data on the production or effects of HPT axis components in normal or malignant cells of the oral cavity. The search identified 221 studies, of which 14 were eligible. Eight studies were retrospective analyses of clinical samples, one study involved both in vivo and in vitro experiments, and the remaining five studies were conducted in vitro using cell lines. The search identified evidence of effects of HPT components on oral cancer cells. However, there were limited data for the production of HPT axis components by oral tissues. We conclude that a possible role of the local HPT axis equivalent in the oral mucosa may not be established at present. The gaps in knowledge identified in this scoping review, particularly regarding the production of HPT components by oral tissues, warrant further investigation.

Does oral lichen planus aggravate the state of periodontal disease? A systematic review and meta-analysis

BACKGROUND

The objective of this systematic review and meta-analysis (SRM) was to assess the evidence between the association of oral lichen planus and periodontal disease, evaluating the periodontal clinical parameters and biomarkers levels.

METHODS

This systematic review and meta-analysis followed PRISMA and was registered in PROSPERO (CRD42020181513). Searches were accomplished in databases for articles published until June 2021. The meta-analysis was performed with the variables: plaque index (PI), gingival index (GI), probing depth (PD), and clinical attachment loss (CAL). The mean difference was applied with a 95% confidence interval.

RESULTS

Six articles were included. Qualitative analysis showed the levels of biomarkers (matrix metalloproteinases, interleukins, and periodontal microbiological profile) are increased in subjects with periodontal disease and oral lichen planus. In the meta-analysis, these subjects also presented increases in all periodontal clinical parameters evaluated: GI-gingivitis 0.22 [0.14, 0.31] p < 0.0001 and periodontitis 0.12 [0.06, 0.19] p = 0.0003; PI-gingivitis 0.22 [0.12, 0.31] p < 0.0001 and periodontitis 0.15 [0.08, 0.23] p < 0.0001; PD-gingivitis 0.27 [0.06; 0.48] p = 0.0107 and periodontitis 0.11 [0.01; 0.21] p = 0.0299; and CA-periodontitis 0.06 [0.01, 0.12] p = 0.0176.

CONCLUSIONS

Evidence suggests a significant relationship between the severity of periodontal disease and the presence of oral lichen planus. Although the association is biologically plausible, further studies are needed using populations and well-defined biochemical and clinical outcomes with consideration of potential confounding factors.

CLINICAL RELEVANCE

This SRM provides information on the interaction between OLP and periodontal disease and guides clinicians to make evidence-based decisions and suggests recommendations for further high-quality studies.

No detection of TSH or TSHR in oral lichen planus lesions in patients with or without hypothyroidism

Objective: An association between hypothyroidism (HT) and oral lichen planus (OLP) has been reported. However, the mechanisms that could explain this association remain unresolved. This study aimed to evaluate the expression of thyroid-stimulating hormone (TSH) and thyroid-stimulating hormone receptor (TSHR) in healthy oral mucosa and in OLP lesions of individuals with and without HT.Material and methods: Immunohistochemical expression of TSH and TSHR was studied in oral mucosal biopsies obtained from 14 OLP patients with HT, 14 OLP patients without HT and 10 healthy controls without oral mucosal lesions. Gene expression of TSHR was investigated by using three different PCR techniques in oral mucosal samples from 7 OLP patients with HT, 3 OLP patients without HT, 9 healthy controls and in cultured human oral epithelial cells. Gene expression of TSH was examined by employing 2 PCR techniques in oral mucosal samples from 2 OLP patients with HT, 2 OLP patients without HT and 4 healthy controls.Results: TSH and TSHR stainings were negative in the studied oral mucosal specimens. Gene quantification assays demonstrated negative gene expression of TSH and TSHR in clinical and in vitro samples.Conclusions: These results suggest that TSH and TSHR may not be commonly involved in the pathogenetic mechanism that could explain the association between OLP and hypothyroidism.

Oral lichen planus and thyroid gland diseases: possible associations

Background

Lichen planus (LP) is a chronic inflammatory mucocutaneous disease that commonly affects the oral cavity. Previous reports have suggested a possible association between LP and thyroid gland diseases (TGDs). The purpose of this study was to investigate possible associations between oral lichen planus (OLP) and TGDs.

Methods

Patients diagnosed with OLP, both clinically and histopathologically (N = 102), were classified according to clinical course (symptomatic/asymptomatic), type (reticular/plaque, atrophic and erosive) and location of lesions. Data on TGDs was compared to age- and gender-matched controls (N = 102) without OLP. Diagnosis of any type of TGD and related medication for study and control groups was recorded from the medical files provided by patients’ physicians. Statistical analysis used Student’s t-test and Fisher’s exact test; significance was set at p < 0.05.

Results

TGDs (all), hypothyroidism and related medications were found in 16.6, 12.7 and 12.7% of patients with OLP, respectively. These findings were similar to the control group: TGDs (all) -15.7%, hypothyroidism - 9.8% and thyroid gland disease-related medication - 9.8% (p > 0.05). No significant associations were found between different characteristics of OLP and hypothyroidism or other TGD (p > 0.05).

Conclusions

We found no significant associations between the co-existence of OLP and TGD or related-medications. Our findings are in agreement with some of the previously published similar studies but in controversy with others. Further well-designed, multicenter studies with large groups of patients and controls may help to establish the nature of the associations between OLP and TGDs.

Association of OLP and thyroid disorder: Case report and review of literature

Oral lichen planus is a chronic T cell mediated inflammatory condition with multifactorial etiology. Being autoimmune mediated condition, it has been associated with other autoimmune disorders. This case report discusses the possible presentation of oral lichen planus in hypothyroid patients as a marker of severity of the thyroid deficient status and the possible pathogenetic link between both the conditions.

Lichen planus and diabetes mellitus: Systematic review and meta-analysis

OBJECTIVE

The aim of this study was to perform a systematic review and meta-analysis answering the following questions: (a) "What is the prevalence and risk of oral lichen planus among patients with diabetes mellitus?" and (b) "What is the prevalence and risk of diabetes mellitus among patients with oral lichen planus?".

MATERIAL AND METHODS

A bibliographic search was conducted in PubMed/Medline and Scopus database from 1966 to March 2018, using the following terms: "Lichen planus" AND "Diabetes mellitus" AND "Prevalence" AND "Oral mucosal lesions".

RESULTS

Twenty-two studies were included in this review. Twelve studies assessed the prevalence of diabetes mellitus among patients with lichen planus. The prevalence reported ranges from 1.6% to 37.7% with a relative risk of 2.432. Ten studies assessed the prevalence of lichen planus among patients with diabetes mellitus which showed a prevalence of lichen planus ranging from 0.5% to 6.1% with a relative risk of 1.4.

CONCLUSIONS

Contradictory results were found when analyzing the relationship between lichen planus and diabetes mellitus. Diverse factors should be considered when studying this association for a correct interpretation of results. Diabetes mellitus has high prevalence and morbidity, which is why new case-control studies are needed to further investigate this association.