CIRCADIAN BLOOD-PRESSURE AND HEART-RATE PROFILES IN NORMOTENSIVE PATIENTS WITH MILD HYPERTHYROIDISM

We investigated the influence of thyroid hormones on the circadian blo od pressure (BP) and heart rate (HR) variations in 12 normotensive sub jects and 12 normotensive patients with mild hyperthyroidism. BP and H R were monitored every 30 minutes for 48h, and electrocardiograms (ECG s) were recorded to measure the RR interval of the ECGs. We analyzed t he circadian BP and HR variations, HR variability and the morning rise in BP and HR. There was no significant difference in the average 24h BP between groups. HR and pulse pressure were higher in the hyperthyro id group than in the control group. Though the circadian BP pattern wa s similar in both groups, HR decreased at night in the control group, but not in the hyperthyroid group. Spectrum analysis of the RR interva l showed no increase in the high-frequency (HF) component at night in patients with hyperthyroidism. The HR did not show a morning rise in t he hyperthyroid group. These findings indicate that the circadian rhyt hm of HR was not preserved in patients with mild hyperthyroidism. The circadian BP rhythm was similar in normotensive subjects and normotens ive patients with mild hyperthyroidism, suggesting that it resulted fr om factors other than thyroid hormone.