Introduction: The aim of the study was to evaluate the effects on serum insulin and serum thyroid profile of a dietary supplement, myo-inositol, given alone or in combination with melatonin to women during menopausal transition.Methods: Forty women aged 45-55 years and at least 6 months of amenorrhea were enrolled in this study. They were randomly assigned to two groups of 20 each. One group took myo-inositol (myo-Ins) (2g twice a day) and the other group took 2g/d myo-Ins plus 3g/d melatonin before sleeping. At the beginning of the study and after 6 months, all women were evaluated for the following indices: waist circumference, body mass index, blood pressure, endometrial thickness, as well as serum concentrations of TSH, FT3, FT4 and insulin.Results: Both at baseline and at 6 months, the two groups were statistically similar for each of the considered indices. If percent changes (%, 6 months over baseline) are contrasted in the two groups, serum TSH decreased in the myo-Ins group but increased in the latter, while serum insulin decreased in both groups.Conclusions: The combination of myo-Ins plus melatonin seems to affect positively glucose metabolism, while myo-Ins only seems to improve thyroid function.