A tendency for a reduction in the circulating, saliva and gingival crevicular fluid levels of adiponectin in periodontitis in human studies, particularly those with co-existing obesity and type 2 diabetes mellitus, can be demonstrated but these finding are often disparate due to variable methods in case definitions, assay techniques, metabolic background of subjects and other confounders. The gene discussed is ADIPOQ; the disease is periodontitis.