TSH Is Associated With Blood Pressure in Hypertension- Regardless of Etiology and The DASH Diet and Nocturnal Dipping: Does Ethnicity Matter?

TSH Is Associated With Blood Pressure in Hypertension—Regardless of Etiology

There are many determinants of blood pressure. It has long been recognized that multiple endocrine systems play a role. For example, primary aldosteronism (PA) is the most common hormonal cause of hypertension. Thyroid-stimulating hormone (TSH) has also been shown to bear a continuous relationship to blood pressure in both normotensive and hypertensive subjects. In addition, ultrasound has revealed a higher than expected prevalence of abnormalities of the thyroid gland in patients with PA—and higher than that found in patients with essential hypertension (EH).

Federica Turchi and colleagues in Ancona, Italy, examined TSH levels and blood pressure in patients with EH and PA and also determined the prevalence of thyroid disease in PA subjects. They report that the relationship between elevated blood pressure and TSH levels was similar in PA and EH subjects, although both were higher in those with PA. Thyroid-function abnormalities were similar in the two groups. By contrast, the prevalence of morphological abnormalities of the thyroid (multinodular goiter, solitary goiter, and papillary cancer) were more frequent in PA than EH subjects (66% vs. 46%, P < 0.05). The authors note that this study is the first demonstration of a parallel relationship between TSH and blood pressure in PA patients, a relationship similar to that seen in EH. The explanation for this association could not be determined in this observational study. However, what can be inferred from this work is that the relationship of TSH to blood pressure is likely to be continuous in all patients with hypertension, regardless of its etiology. See page 12741

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Office diastolic blood pressure (a) daytime diastolic blood pressure and (b) night-time diastolic blood pressure values across TSH quartiles in patients with PA. DBP, diastolic blood pressure; dt, daytime; nt, night-time; PA, primary aldosteronism; TSH, thyroid-stimulating hormone. 1: first TSH quartile (TSH between 0.01 and 0.96 mUI/l); 2: second TSH quartile (TSH between 0.97 and 1.48 mUI/l); 3: third TSH quartile (TSH between 1.49 and 1.94 mUI/l); 4: fourth TSH quartile (TSH between 1.95 and 10.7 mUI/l). *P = 0.01 between first and fourth quartile. °P = 0.01 between first and fourth quartile. P < 0.05 between first and fourth quartile.

The DASH Diet and Nocturnal Dipping: Does Ethnicity Matter?

Blood pressure—whether measured in a population survey or in the physician’s office—has a robust association with subsequent cardiovascular outcomes for groups, but is a poor predictor for individuals. Hence, the search for ways to assess blood pressure that produce more precise estimates of outcomes for individuals remains a lively arena of investigation. The fall of blood pressure during sleep, known as nocturnal dipping, is one dimension of the dynamic pressure pattern that may be more predictive of strokes and heart attacks than either individual or 24-hour recordings. Blunting of the usual fall in systolic pressure is associated with poor outcomes. American blacks, whose cardiovascular disease experience is more severe than that of American whites, are more likely to have blunted dipping.

As reported in this issue, Aric Prather and colleagues at Duke University and the University of North Carolina at Chapel Hill analyzed 24-hour blood pressure recordings over 4 months in 43 black and 75 white overweight hypertensive subjects randomized to either the DASH (Dietary Approaches to Stop Hypertension) diet, which is low in fat and high in fruit and vegetables, or their usual diet. Blacks were more likely than whites to have blunted dipping at baseline. However, the black subjects were more likely than the white subjects to have significant improvement in nocturnal dipping when allocated to the DASH diet. For those on the DASH diet, an increase in potassium intake was similar in both ethnic groups and therefore does not appear to explain the findings. The authors caution that these comparisons were in groups not equalized by randomization and thus are observational findings that remain subject to experimental confirmation. However, if these ethnic differences are confirmed and explained, they may have important implications for clinical application of the DASH diet. See page 1338

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About the Author: Tung Chi