Dermatology ยท Medical Literature
Effects of Treatment with L-Thyroxine on Chronic Urticaria in Subjects with Autoimmune Thyroiditis: A Systematic Review and Meta-Analysis.
Abstract
Chronic urticaria (CU) is a condition characterized by recurrent wheals/angioedema lasting longer than 6 weeks. It is treated in a stepwise manner, starting with antihistamines and escalating to more advanced therapies, if needed. It is frequently associated with autoimmune thyroiditis (AT), and thyroid autoantibodies and thyroid-stimulating hormone (TSH) may contribute to the severity of symptoms, though the exact pathogenesis remains unclear. We performed a systematic search on Scopus and Pubmed databases, finding nine studies published between 1989 and 2018. Five studies were therefore included in our meta-analysis, and we found that the treatment with L-thyroxine (LT4) is associated with a significant improvement in CU symptoms (sMD -2.31, 95% CI -2.98 to -1.64; p < 0.00001). However, when compared with placebo or standard care, LT4 did not demonstrate superiority in terms of symptom scores. It is unclear whether it provides greater benefit in individuals with normal thyroid function or hypothyroidism, or whether it is more effective when used as suppressive or replacement therapy. Therefore, evidence for LT4 treatment improving urticaria is conflicting, with uncertain benefit prompting further evaluation and in-depth study of the molecular mechanisms and markers linking CU and AT.
Clinical relevance
Chronic urticaria (CU) affects a significant subset of patients with concurrent autoimmune thyroiditis (AT), a population in whom standard stepwise antihistamine therapy may yield suboptimal control, raising the question of whether thyroid-directed therapy could modify disease course. Thyroid autoantibodies and elevated TSH have been implicated in urticaria severity, yet no clear mechanistic or therapeutic consensus exists. This systematic review and meta-analysis addresses a clinically relevant gap by synthesizing available evidence on L-thyroxine (LT4) as an adjunctive or alternative treatment strategy in this comorbid population.
Key findings
1. Nine studies published between 1989 and 2018 were identified via systematic search of Scopus and PubMed databases, with five meeting inclusion criteria for quantitative meta-analysis. 2. LT4 treatment was associated with a statistically significant improvement in CU symptom scores overall (standardized mean difference [sMD] -2.31, 95% CI -2.98 to -1.64; p < 0.00001), indicating a large pooled effect size. 3. When LT4 was compared directly against placebo or standard care in controlled analyses, it did not demonstrate statistically significant superiority in symptom score outcomes. 4. It remains unresolved whether LT4 confers greater benefit in euthyroid patients versus those with overt or subclinical hypothyroidism, representing a critical patient-selection knowledge gap. 5. The differential efficacy of suppressive versus replacement LT4 dosing strategies could not be determined from the available data. 6. The overall body of evidence is characterized as conflicting and limited, with uncertain net clinical benefit, precluding definitive practice-changing recommendations at this time.
Practice implications
Clinicians managing CU patients with confirmed AT and poorly controlled symptoms despite optimized antihistamine therapy may consider a time-limited trial of LT4, particularly given the significant within-group symptom improvement signal (sMD -2.31), though they should counsel patients that controlled comparisons do not yet confirm superiority over standard care. Patient selection, optimal dosing strategy (suppressive vs. replacement), and thyroid function status at initiation remain undefined, necessitating individualized shared decision-making and close monitoring of both urticaria activity scores and thyroid function tests during any trial of LT4. Pending higher-quality randomized controlled trial data, LT4 should not be adopted as a routine adjunct for CU-AT comorbidity outside of a clinical trial or carefully documented off-label context.