I take selenium, but I take it for thyroid eye disease, not the Graves disease itself. My previous endocrinologist and my neuro-ophthalmologist were very supportive of me taking selenium (100mcg a day, now down to 50mcg a day), but it was never offered as an alternative to treating my Graves disease.
The study (http://www.nejm.org/doi/full/10.1056/nejmoa1012985)
[nejm.org] found that “selenium administration significantly improved quality of life, reduced ocular involvement, and slowed progression of the disease in patients with mild Graves' orbitopathy.” Like Kimberly mentioned, the study was done in your country and my endocrinologist knew a few of the Italian researchers and lauded their work.
As Darcy said, selenium is found in a lot of foods we eat, so you may not need a high dose depending on your diet, but I was told it was safe for me to take up to 200mcg a day in supplement form because of my thyroid eye disease (TED).
Most of us here are in the US, UK and Canada, and I don't think we get too many people from Italy. Is selenium common for Italian patients with Graves disease, even if they have no eye involvement?