In male subjects, normal serum alanine aminotransferase levels (less than 20 IU/L) were observed in 95.8% of nonperiodontitis patients and in 4.2% of periodontitis patients, whereas abnormal levels were found in 87.4% of nonperiodontitis patients and in 12.6% of periodontitis patients. This evidence concerns the gene GPT and periodontitis.