Reports in the medical literature describe several cases of acute onset psychosis as a result of hypothyroidism, and a small number related to radioactive iodine treatment (RAIT). The effectiveness of RAIT in the therapy of differentiated thyroid cancer depends on a sufficient TSH level elevation obtained by discontinuing thyroid hormone replacement therapy.

Describing a case of new-onset psychotic disorder in a 42-year-old woman following a RAIT session, one year after total thyroidectomy for papillary thyroid carcinoma developed on multinodular goiter.

Identifying a relation between the psychosis onset and the therapeutic protocol the patient underwent for the thyroid disease treatment.

We present the case of a patient with a medical history of thyroid disease, secondary posttraumatic epilepsy and minor thalassemia; the clinical and paraclinical evaluations; the psychiatric presentation, treatment and evolution.

The overt psychotic symptomatology developed in this case a few days after RAIT and led to an emergency psychiatric hospitalization, the laboratory findings showed a TSH value of 75 microunits/ml. The psychotic episode remitted after a month of antypsichotic medication and levothyroxinum replacement therapy. The patient has been receiving psychotropic medication for a year, during which she was readmitted for a depressive episode (6 months after first discharge).

The patient's psychotic disorder developed after a period of thyroid hormone replacement therapy discontinuation and consecutive to the RAIT session, which indicates that in susceptible individuals there is a risk for psychosis with this therapeutical strategy.