The strongest common genetic risk factor for type 2 diabetes, and the variant that largely decides whether you keep making lactase as an adult.
TCF7L2 and LCT/MCM6. 2 variants covering type 2 diabetes risk and adult lactase persistence.
The Biology
Type 2 diabetes has a substantial genetic component. TCF7L2 is the largest-effect common genetic risk factor for type 2 diabetes identified so far, and its discovery in 2006 was a landmark in the field. Separately, a single variant upstream of the lactase gene largely determines whether lactase production continues after childhood.
What Varia Analyzes
TCF7L2 (rs7903146), where each T allele is associated with higher type 2 diabetes risk through effects on beta-cell insulin secretion; and LCT/MCM6 (rs4988235), where the A allele is associated with lactase persistence and two G alleles with lactase non-persistence.
Why It Matters
Genetic risk at TCF7L2 is one input among many: body weight, physical activity, diet, and age also shape type 2 diabetes risk, and glucose and HbA1c tests show where things stand. Lactase non-persistence is common worldwide and is the usual reason adults digest dairy less easily; the genotype describes enzyme production, not symptoms.
Not in Varia's Catalog
Other metabolic variants often discussed are not in the catalog: KCNJ11 E23K (rs5219), IGF2BP2 (rs4402960), FTO (rs9939609), PPARG Pro12Ala (rs1801282), and MTNR1B (rs10830963). Varia does not read these from your file, so a scan reports nothing about them either way.