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Decreased adrenergic sensitivity in patients with hypothyroidism
R Polikar1, B Kennedy, A Maisel
1Division of Cardiology, University of California-San Diego Medical Center 92103.
Journal of the American College of Cardiology
|January 1, 1990
Summary
Hypothyroidism reduces the heart's response to stress hormones like epinephrine. Thyroid replacement therapy normalizes this cardiovascular sensitivity, improving heart rate regulation in hypothyroid patients.
Area of Science:
- Cardiology
- Endocrinology
- Pharmacology
Background:
- Hypothyroidism is associated with cardiovascular alterations.
- Catecholamine sensitivity plays a crucial role in heart rate regulation.
- Understanding these interactions is vital for managing hypothyroid patients.
Purpose of the Study:
- To investigate the cardiovascular sensitivity to catecholamines in hypothyroid patients.
- To assess the impact of thyroid replacement therapy on this sensitivity.
- To correlate heart rate responses with plasma catecholamine levels.
Main Methods:
- Assessed cardiovascular response to isoproterenol in hypothyroid and euthyroid states.
- Utilized 24-hour ambulatory ECG monitoring for heart rate assessment.
- Measured plasma epinephrine and norepinephrine levels before and after treatment.
Main Results:
- Hypothyroid patients showed a significantly reduced heart rate increase in response to isoproterenol compared to euthyroid individuals.
- Basal and maximal heart rates were lower in hypothyroid patients, despite higher norepinephrine levels.
- Thyroid replacement therapy normalized the cardiac response to isoproterenol.
Conclusions:
- Patients with hypothyroidism exhibit diminished cardiac chronotropic response to beta-adrenergic stimulation.
- This reduced sensitivity may explain the lower basal and maximal heart rates observed in hypothyroidism.
- Thyroid hormone status critically influences cardiovascular adrenergic responsiveness.