Background: At present, hypothyroidism is a well-known risk factor for cardiovascular disorders. The aim of this study was to assess the effects of hypothyroidism on cerebral blood flow velocity with transcranial Doppler (TCD) ultrasonography.
Design and methods: In this study, 30 subjects were enrolled for clinical, subclinical, and healthy control groups. Bilateral middle cerebral artery (MCA) peak-systolic, end-diastolic, and mean blood flow velocities; Gosling's pulsatility index values; and Pourcelot's resistance index values were recorded and compared with each other. TCD was performed in clinical hypothyroid patients after they became euthyroid with thyroid hormone replacement therapy (HRT). The initial and post-HRT results for the clinical hypothyroid group were then compared and evaluated.
Results: There were 30 subjects in each group. Men/women ratio and mean age in clinical hypothyroid, subclinical hypothyroid, and control groups were 3/27, 4/26, and 5/25, and 37.4, 34.4, and 36.7 respectively. Peak-systolic, end-diastolic, and mean blood flow velocities of bilateral MCA were similar in clinical and subclinical hypothyroid groups but significantly higher when compared with the control group. After adequate thyroid HRT in clinical hypothyroid group, the peak-systolic, end-diastolic, and mean blood flow velocities were significantly decreased.
Conclusions: Increased cerebral blood flow velocities were observed in clinical and subclinical patients with hypothyroidism. The normalization of increased blood flow velocity with thyroid HRT suggests a reversible condition.