This paper addresses the issue of (recurrent) mania in relation to an increased T4-value, whether or not influenced by lithium. Lithium has an anti-TSH-effect on the thyroid gland by inhibiting the intracellular enzyme adenylate cyclase. This might cause hypothyroidism. Moreover, lithium is also known to have a direct stabilizing effect on (behavioral manifestations) of dopamine receptor supersensitivity.
The hypothesis regarding the relation between thyroid function and affective disturbances is that the altered thyroid function may cause a change in the availability of the central dopamine receptors. Dopamine is known to be able to cause a manic state. TSH and TRH are also involved in this mechanism. It is, therefore, very likely that an increased thyroid function, whether or not caused by discontinuation of lithium-therapy, could induce a (recurrent) mania.
