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Thyroid function and blood pressure homeostasis in euthyroid subjects.
Olga Gumieniak1, Todd S Perlstein, Paul N Hopkins
1Endocrinology, Diabetes and Hypertension Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, 221 Longwood Avenue, RFB-2, Boston, MA 02115, USA.
The Journal of Clinical Endocrinology and Metabolism
|July 9, 2004
Summary
Thyroid hormone levels influence blood pressure regulation even in euthyroid individuals. Lower free thyroxine index (FTI) and higher TSH are linked to hypertension and salt sensitivity.
Area of Science:
- Endocrinology
- Cardiovascular Physiology
- Hypertension Research
Background:
- Overt and subclinical hypothyroidism are linked to elevated systemic vascular resistance and hypertension.
- Thyroid dysfunction's impact on blood pressure is well-established, but its role in euthyroid individuals requires further investigation.
Purpose of the Study:
- To investigate the relationship between thyroid function and blood pressure homeostasis in euthyroid individuals.
- To determine if thyroid hormone levels predict blood pressure salt sensitivity.
Main Methods:
- Assessed blood pressure responses to high- and low-sodium diets in 284 subjects (68% hypertensive).
- Measured serum free thyroxine index (FTI) and TSH levels.
- Estimated effective renal plasma flow using p-aminohippuric acid clearance to calculate renal vascular resistance (RVR).
Main Results:
- Hypertensive euthyroid subjects had lower FTI (P < 0.0001) and higher TSH (P = 0.046) compared to normotensive subjects.
- FTI independently predicted blood pressure salt sensitivity (beta = -1.51, P < 0.0001).
- FTI correlated negatively with RVR, while TSH correlated positively with RVR on both high- and low-salt diets.
Conclusions:
- Thyroid function influences blood pressure homeostasis within the euthyroid range.
- Lower FTI and higher TSH in euthyroid individuals are associated with hypertension and predict blood pressure salt sensitivity.
- Thyroid hormone likely affects peripheral vasculature, contributing to blood pressure regulation.