*3.1. Study Population*

From the 168 subjects screened, 44 were not included due to the established exclusion criteria, so the study group was composed of 124 DS subjects (Table 1 and Table S2). After evaluating their periodontal status, their distribution was: 62 with a periodontal health (50.0%), 34 with gingivitis (27.4%) and 28 with periodontitis (22.6%).



**Table1.**Demographiccharacteristicsforeachstudygroup,withtheappropriatecomparisons.

standard deviation; min, minimum; max, maximum; fem, female.\* Statistically significant differences.

SD,

Differences in age among groups were statistically significant (*p* < 0.01), since patients with periodontitis (mean age 27.9 years) were significantly older than those with periodontal health (mean age 21.4 years; *p* = 0.01) or with gingivitis (mean age 22.6 years; *p* < 0.01). No significant differences were detected for gender, number of co-morbidities and presence of cardiovascular conditions.

Conversely, statistically significant differences among groups (p = 0.01) were detected for presence of hypothyroidism and intake of supplemental thyroxine medication (levothyroxine). Hypothyroidism was significantly less prevalent in periodontitis subjects (10.7%), when compared with periodontally healthy (41.9%; p = 0.01) and gingivitis subjects (40.3%; p = 0.01).
