Mishari T Alrubaiaan, Ajlan Hashim Alajlani, Raneem Alwatban, Abdulelah Nabil Alkadi, Hawra Fahad Alkhodairy, Fatimah Moayed Alalwan, Sarah Waleed Bin Rashid, Waleed Alajroush
Introduction: Systemic isotretinoin is extensively used to treat moderate-to-severe acne vulgaris and may have systemic endocrine effects through the hypothalamic-pituitary-thyroid axis. Objectives: To investigate the changes in thyroid hormone levels after commencement of systemic isotretinoin among patients with acne vulgaris. Methods: A PubMed, ScienceDirect, Scopus, and Cochrane Library search was performed. Pooled analysis was conducted utilizing Review Manager (RevMan 5.4.1). Results: A total of 447 patients from eight observational studies were included. After three and four months, no increase in TSH levels was observed following isotretinoin treatment with a standardized mean difference (SMD) of 0.09 (95% CI: -0.27–0.46; P=0.62) and (SMD=0.72; 95% CI: -0.01–1.45; P>0.05), respectively. However, a significant increase in TSH levels was observed at six months (SMD=0.54; 95% CI: 0.05–1.03; P=0.03). T4 levels showed no alteration at three months (SMD= −0.24; 95% CI: -0.56–0.08; P=0.14) but were reduced at four months (SMD= -0.79; 95% CI: -1.20– -0.38; P=0.0001) and six months (SMD= -0.87; 95% CI: -1.57– -0.17; P=0.01). T3 levels were reduced at three months (SMD= -0.42; 95% CI: -0.80– -0.04; P=0.03), four months (SMD= -0.63; 95% CI: -1.03– -0.23; P=0.002), and 6 months (SMD= -1.13; 95% CI: -1.77– -0.55; P=0.0001). Conclusion: Long-term isotretinoin treatment may cause time-dependent changes in thyroid hormone levels.