NOS3 and Schnyder corneal dystrophy: Thus to explore the possible association of eNOS gene polymorphism with age of onset of menarche in SCD females, 3 important eNOS gene polymorphisms- eNOS 4a/b, eNOS 894G>T (rs1799983) and eNOS-786 T>C (rs2070744) and plasma nitrite levels were tested among three groups of females- SCD late menarche, SCD early menarche and control females.