Association of Hypertension and Hyperthyroidism in a Subspecialty Clinic and a National Database

Ana M. Rivas, MD; Jeff Dennis, PhD; Camilo Pena, MD; Jonathan Kopel, BS; Kenneth Nugent, MD

Disclosures

South Med J. 2020;113(12):607-611. 

In This Article

Results

During the 6-year period, 414 new patients were referred for evaluation of hyperthyroidism to the endocrinology outpatient clinic, all charts were reviewed for eligibility, and 300 were excluded from further analysis. The final cohort included 96 patients; 77% were female, and the mean age was 43 years (range 18–84). Forty-eight patients (50%) had high blood pressure, and there were no significant differences in body mass indices or in hemoglobin, serum calcium, or thyroid hormone levels between the hypertensive and normotensive groups (Table 1). All of the hypertensive patients had high systolic blood pressure, but only 12 (25%) had high diastolic blood pressure, concomitantly. None of the patients with normal systolic blood pressure had high diastolic blood pressure. When classifying patients by age, the prevalence of high blood pressure was higher in older age groups, despite older patients having lower thyroid hormone levels (Table 2). The prevalence of high blood pressure also was higher than that of the general US population of different age groups (Table 3).[2]

The comparison US adult sample from NHANES is described in Table 4. Approximately 14% of the sample had high blood pressure, and nearly 30% report having been told by a doctor they have high blood pressure. Adjusted ordinary least squares regression indicates a significant positive relationship between FT3 and systolic blood pressure, such that systolic blood pressure increases about 2 U with each unit increase in FT3 (Table 5). Neither low nor high TSH or FT4 levels, respectively, were significant predictors of systolic blood pressure relative to their respective normal reference groups (results not shown). Using FT3 as a categorical variable (low, normal, high) fits the variation in systolic blood pressure slightly better than the linear form and suggests that much of the relation between FT3 and systolic levels is for elevated FT3 compared with normal FT3 levels. Participants with FT3 levels >3.9 pg/mL have a systolic blood pressure 4.86 U higher than those in the normal FT3 range. Levothyroxine use was negatively associated with systolic blood pressure, but did not alter the relation between FT3 and systolic blood pressure levels. A relatively small number of individuals (N < 10) with high FT3 report taking levothyroxine.

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