Evaluation of Cerebral Blood Flow Alterations in Patients with Induced Hypothyroidism

Purpose: In this study; it was aimed to show the affect of induced hypothroidism on regional cerebral blood flow. Material and Methods: In our study, 33 total or near total thyroidectomy patients with welldifferentiated thyroid carsinomas who admitted to our department for I-131 therapy between December 2006 and January 2008 were included. The mean interval for diagnosing hypothyroidism was 32.06± 11.12 day and the mean TSH level was 69.41±28.48 [JlU/ml. Tc-99m HMPAO (heksametil propilenamin oksim) brain SPECT images were taken. Euthyroidism was established 6-8 weeks after application of ablation therapy and L-thyroxin suppression treatment, and Tc-99m HMPAO brain SPECT studies were repeated. The reconstructed brain SPECT images were evaluated with SPM2 (statistical parametric mapping 2) method. The activity in ROI s (region of interest) taken from bilateral region of prefrontal, limbic, parietal, occipital, temporal and global brain were divided to voxel numbers in same ROI and mean signal rate were obtained. All ratios were assessed statistically. Results: In brain SPECT images that were analyzed using SPM2 method, no significant change between hypothyroidic and euthyroidic period was detected. Conclusion: It is demonstrated that induced short-term period of hypothyroidism does notalter regional cerebral blood flow.