Hypothyroidism is a medical condition commonly found in a variety of clinical settings. Physical complaints of thyroid hormone deficiency are many, and psychiatric symptoms include cognitive dysfunction, affective disorders and psychosis.

To study the possible relationship between psychotic symptoms and secondary to treatment with radioiodine hypothyroidism, presenting a case report.

We report a 32 year-old woman without known significant past medical history (except Graves Basedow disease with no current treatment) that came to clinical attention due to psychotic symptoms. The patient was admitted to the hospital and laboratory values revealed hypothyroidism secondary to treatment with radioiodine (which was required six months before for a Graves Basedow disease). We considered the possibility that thyroid dysfunction was the cause of the psychiatric symptoms.

After giving neuroleptic treatment with increasing doses of risperidone (up to 9 mg/day), clinical improvement was observed, with a diminishment of psychiatric symptoms. At the same time, supplementary treatment with thyroid hormone was given, which did not manage to normalize the hormone function at the moment of discharge.

In our patient we cannot establish a definite link between psychotic and clinical thyroid dysfunction, because six months after replacement therapy the hormonal function has not yet been completely standardized. The patient was psychopathologically stable (although treatment was maintained with quetiapine 600 mg/day). There is no doubt that thyroid hormone plays a key role in the regulation of mood, cognition and behavior; we must not ignore this, and always check thyroid function in psychiatric patients.