GLA and osteoporosis: Serum Gla-OC is used as a marker of bone formation, whereas serum ucOC is used as a marker of vitamin K deficiency and as a predictor of hip fracture risk independently of femoral neck bone mineral density [2]; the cut-off value of 4.5 ng/mL for ucOC has been validated [3] and is generally accepted in the selection of Japanese patients for medication for osteoporosis.