<p>Objective: Possible mechanisms regarding the relationship between Hashimoto’ thyroiditis (HT) andperiodontal disease were suggested to be the autoimmune mechanisms. The aim is to report the oral andperiodontal health status of a sample of adolescents with HT; and to investigate the correlations betweenthe clinical periodontal and metabolic parameters of the adolescents with/without HT.Material- Method: Sixty adolescent girls aged between 12-18 years (mean±SD: 15.03±2.05 years) haveparticipated. The study population was comprised of HT (n = 30) and control (C, n = 30) groups. In additionto the endocrinologic evaluations (metabolic parameters) and intra- and extra-oral examinations,periodontal examination including the recording of percentage of bleeding on probing (BOP %), gingivalindex (GI), plaque index (PI), and pocket depth (PD) was made.Results: Except the significantly higher anti-thyroid peroxidase (Anti-TPO) values in HT group than the Cgroup (P = 0.001), none of the metabolic parameters have shown significant differences (P &gt; 0.05). All ofthe subjects had gingivitis. The periodontal parameters were found not significantly different (P &gt; 0.05).Salivary flow rate (SFR) has negative significant correlation with Anti-TPO (r = -0.367, P = 0.046), andcortisol has negative significant correlation with pocket depth (PD) (r = -0.378, P = 0.040).Conclusions: Significant correlations between gingival index (GI) and fT4, and PD and fT4 have led us toconsider that the periodontal inflammation might relate to HT. The adolescence period should also kept inmind; which results in exaggerated host response to the dental plaque, and projected with the presence ofgingivitis in the whole study population.<br></p>