The effects of lithium discontinuation and the non-effect of oral inositol upon thyroid hormones and cortisol in patients with bipolar affective disorder.

Thyroid and adrenal function was assessed in euthymic bipolar patients, stable on prophylactic lithium for at least 1 year, before and after lithium discontinuation in a randomised double-blind placebo-controlled trial. All hormonal measurements were within the reference range, but a significant increase (P less than 0.001) in plasma thyroxine (T4) levels and a decrease (P less than 0.01) in TSH levels were observed 1 month after lithium withdrawal; cortisol concentrations showed a non-significant decrease in the same period. No relationship could be demonstrated between the magnitude of the change in hormone levels and the probability of relapse of manic symptoms. In the second part of this study, inositol was added for 11 days to the diets of bipolar patients being treated with prophylactic lithium and normal controls. No modification was shown in T4 and TSH in either group before or after inositol administration. Inositol did not alleviate other side-effects such as tremor and thirst in the patient group. This result suggests that short-term dietary inositol is not equivalent to lithium withdrawal and is of no value in reducing hormonal and other adverse effects of lithium prophylaxis.