Table 4.

Summary of evidence for clinical use of the nutraceuticals reviewed here in the thyroid setting *.

Question: Is There Evidence for Clinical Use of …?	Answer
Carnitine	Currently available evidence supports the usefulness of l-carnitine in hyperthyroid patients. Carnitine ameliorates a number of symptoms and signs, including cardiac arrhythmia. Case reports have shown benefits even in the setting of thyroid storm. However, no changes in thyroid function tests were reported. One practical setting for the use of l-carnitine (two grams per day) is the control of hyperthyroidism symptomatology when the patients need to take low doses of antithyroid drugs. Only one Korean study is currently available for hypothyroidism, thus precluding conclusions.
Inositols	Only in one study, MI alone (2 g twice a day) or MI plus melatonin (2 g/d MI plus 3 g/d melatonin) were given in two groups of euthyroid postmenopausal women, and serum FT4 and TSH evaluated. MI alone caused an almost 3.5% increase in serum FT4 and a 10% decrease in serum TSH. This contrasted with the opposite changes (3.5% decrease in serum FT4 and almost 10% increase in serum TSH) observed in the group under MI plus melatonin. Few studies have been conducted only in one Western country (Italy), and with the combination of MI plus selenium or MI plus carnitine. Supplementation with the first combination has been used in the setting of patients with Hashimoto’s thyroiditis related SCHypo, and it decreased both serum thyroid autoantibodies and TSH. The combination of MI plus carnitine was only investigated in one study of patients with SCHyper, thus precluding conclusions.
Melatonin	There has been interest in melatonin and autoimmunity and the thyroid gland has been implicated in the discussion. It is thought that melatonin may have a paracrine role and in thyroid disease under a condition of oxidative stress may reduce the processes involved in thyroid antoimmunity. However, there are no controlled trials or definite data to show conclusively that melatonin can be beneficial in thyroid disease.
Resveratrol	No answer can be given, simply for lack of studies.
Selenium	Benefits have been demonstrated for mild forms of Graves’ ophthalmopathy. Benefits for the clinical course of GD itself are controversial. In the setting of HT, a benefit has been shown more on serum thyroid autoantibodies than on thyroid function. There is only one study on the benefit given by selenium supplementation, both in terms of serum thyroid autoantibodies and thyroid dysfunction, in the setting of PPT. For the combinations of selenium with MI see above.

Abbreviations, in alphabetical order: GD = Graves’ disease; HT = Hashimotos’ thyroiditis; MI = myo-inositol; PPT = postpartum thyroiditis. SCHyper = subclinical hyperthyroidism; SCHypo = subclinical hypothyroidism.