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The circadian variation of blood pressure and heart rate in patients with hyperthyroidism
1Second Department of Internal Medicine, Tohoku University School of Medicine, Sendai.
Insights
This study found that severe hyperthyroidism disrupts the normal nocturnal fall in blood pressure (BP) and heart rate (HR). Excess thyroid hormone significantly impacts circadian BP variations, particularly systolic pressure.
Area of Science:
- Endocrinology
- Cardiovascular Physiology
- Chronobiology
Background:
- Circadian variations in blood pressure (BP) and heart rate (HR) are crucial for cardiovascular health.
- Hyperthyroidism, a condition of excess thyroid hormone, may influence these circadian rhythms.
- Beta-blockers are commonly used to manage hypertension and hyperthyroidism symptoms.
Purpose of the Study:
- To investigate the impact of hyperthyroidism and beta-blocker treatment on the circadian variation of BP and HR.
- To determine the relationship between thyroid hormone levels and nocturnal BP/HR patterns.
Main Methods:
- Ambulatory blood pressure monitoring (UBP-100) was used to measure BP and HR every 5 minutes over 24 hours.
- Participants included normal subjects, patients with essential hypertension on beta-blockers, and patients with hyperthyroidism (some on beta-blockers).
Main Results:
- A normal nocturnal fall in BP and HR was observed in healthy subjects, hypertensive patients on beta-blockers, and those with mild-to-moderate hyperthyroidism.
- Severe hyperthyroidism was associated with a diminished nocturnal fall, affecting HR alone and with reduced amplitude.
- A significant negative correlation was found between triiodothyronine (T3) levels and the amplitude of the nocturnal systolic BP fall.
Conclusions:
- Excess thyroid hormone, particularly in severe hyperthyroidism, significantly modulates the circadian variation of blood pressure and heart rate.
- The nocturnal fall in systolic blood pressure is negatively influenced by elevated triiodothyronine levels.
- These findings highlight the importance of thyroid hormone regulation in maintaining normal cardiovascular circadian rhythms.
Abstract:
The circadian variation of blood pressure (BP) and heart rate (HR) was examined in 18 normal subjects, 15 patients with essential hypertension treated with beta-blockers and 21 patients with hyperthyroidism. Most of the patients with hyperthyroidism were also treated with beta-blockers. The 24 hr BP was measured with an ambulatory blood pressure monitoring device (UBP-100) every 5 min. A nocturnal fall in BP and HR was observed in the patients with essential hypertension treated with beta-blockers and the patients with mild to moderate hyperthyroidism as well as normal subjects. On the other hand, in patients with severe hyperthyroidism the nocturnal fall was observed in HR alone, and the fall was small in its amplitude. There was a significant negative correlation between triiodothyronine (T3) level and percentage amplitude of the nocturnal fall in systolic BP (n = 21, r = -0.5, p less than 0.01). However, this relation was not significant in diastolic BP and HR. These results indicate that excess thyroid hormone may modulate the circadian variation of BP and HR.