Myo-Inositol is classified as a member of the vitamin B complex. It is a constituent of living cells and is widespread in many food. It is involved in a number of biological processes, including insulin signal transduction, resulting in modulating insulin sensitivity. One hundred post-menopausal women from 50 to 60 years old, affected by metabolic syndrome (criteria are described in NIH ATP III) will be randomized into two groups: 50 treated with myo-inositol 2 g twice per day and fifty treated with metformin for six months. Metformin is the drug usually used in diabetic and pre-diabetic conditions, as metabolic syndrome. The investigators hypothesize that the administration of myo-inositol would improve the insulin-receptor activity in these women, reducing insulin resistance as well as metformin.