Hyperprolactinemia-Associated Bilateral Breast Uptake in Nonlactating Breasts on Radioiodine Scans with SPECT/CT Correlation: Diagnostic Pitfalls in Patients Receiving Atypical Antipsychotic Therapy

Abstract Hyperprolactinemia is a common endocrine disorder often induced by antipsychotic medications through dopaminergic inhibition. We report two nonlactating women on long-term atypical antipsychotics of risperidone with trifluperazine and olanzapine. They showed incidental bilateral breast uptake on radioiodine scans. One had markedly elevated serum prolactin; the other had high-normal levels. This finding reflects prolactin-mediated upregulation of the sodium/iodide symporter (NIS) in breast tissue, independent of lactation. Awareness of this mechanism is essential to avoid misinterpretation of radioiodine imaging as pathological uptake. These cases underscore the importance of correlating imaging findings with patient medication history and prolactin status in interpreting iodine scans.