To investigate the relationship between thyrotropin concentrations within the accepted reference range and cardiovascular risk.
Initially, 728 women aged 45-60 years were enrolled over a 12-month period. All participants underwent full cardiovascular assessment, including detailed health questionnaire, sphygomanometry, body mass index (BMI) calculation, fasting glucose and lipid profiling, and measurement of serum thyrotropin concentrations. Patients whose thyrotropin concentrations were within the reference range (0.5-4.5 mU/L) were divided into quartiles (n = 629). The means of cardiovascular risk parameters between the first (n = 158) and fourth (n = 157) quartile were compared. Subsequently, the relationships between thyrotropin concentration and risk parameters for cardiovascular disease were examined.
This study demonstrates that, within the reference range, increasing thyrotropin concentrations are associated with increasing risk parameters for the development of cardiovascular disease. Subjects with thyrotropin concentrations within the uppermost quartile of the reference range had significantly increased waist circumference, BMI, glucose, triglyceride, and systolic blood pressure measurements when compared to those in the lowermost quartile. Furthermore, significant relationships between thyrotropin and waist circumference, BMI, and fasting glucose and triglycerides concentrations were demonstrated. Finally, independent relationships between thyrotropin and both fasting glucose and triglyceride concentrations were demonstrated.
Within the reference range, increasing thyrotropin concentrations are associated with increasing cardiovascular risk parameters. Fasting glucose and triglycerides have been shown to be independently associated with thyrotropin concentration.
"However, the practice of measuring TSH levels twice and applying more stringent exclusion criteria made the impact of an acute setting or heart disease minimized. In addition, most of studies on thyroid function that have been published have adopted measuring TSH levels at one time point [6,7,10]. Third, the power of the present study could have been stronger with a larger number of study subjects. "
[Show abstract][Hide abstract] ABSTRACT: The relationship between TSH and the lipid profile is contradictory because few studies have excluded the potential influence of the thyroid hormones (TH). The aim of the present study was to evaluate the relationship between serum TSH levels and the lipid profile independent of TH.
1302 CHD patients diagnosed by coronary angiography were retrospectively studied. The prevalence and distribution of thyroid dysfunction were analyzed first. To assess the impact of TSH on serum lipids, Pearson's correlation analysis was performed after adjustments for classic factors and TH. To calculate the extent of the effect of TSH on the serum cholesterol level, the partial least squares method and additional statistical methods were used.
After the exclusions, a total of 568 patients (270 males and 298 females with a mean age of 63.56 ± 11.376 years) were selected. The prevalence of thyroid dysfunction among the patients was 18.66%, and the prevalence of hypothyroidism (15.32%) was higher than that of hyperthyroidism (3.34%). Even after adjusting for confounding factors, such as sex, age, smoking status, fasting plasma glucose levels and TH, a significant positive impact of TSH on the serum total cholesterol (TC) level was revealed (r = 0.095, p = 0.036). Each 1 mIU/L increase in the TSH level might be linked to a 0.015580712 mmol/L elevation of the serum TC value.
TSH can increase the TC level in CHD patients independent of TH. The present study suggests a potential physiological role of TSH and the importance of maintaining an appropriate TSH level in CHD patients.
[Show abstract][Hide abstract] ABSTRACT: Data on the association between subclinical thyroid dysfunction and coronary heart disease (CHD) and mortality are conflicting.
To summarize prospective evidence about the relationship between subclinical thyroid dysfunction and CHD and mortality.
MEDLINE (1950 to January 2008) without language restrictions and reference lists of retrieved articles were searched.
Two reviewers screened and selected cohort studies that measured thyroid function and then followed persons prospectively to assess CHD or mortality.
By using a standardized protocol and forms, 2 reviewers independently abstracted and assessed studies.
Ten of 12 identified studies involved population-based cohorts that included 14 449 participants. All 10 population-based cohort studies examined risks associated with subclinical hypothyroidism (2134 CHD events and 2822 deaths), whereas only 5 examined risks associated with subclinical hyperthyroidism (1392 CHD events and 1993 deaths). In a random-effects model, the relative risk (RR) for subclinical hypothyroidism for CHD was 1.20 (95% CI, 0.97 to 1.49; P for heterogeneity = 0.14; I(2 )= 33.4%). Risk estimates were lower when higher-quality studies were pooled (RR, 1.02 to 1.08) and were higher among participants younger than 65 years (RR, 1.51 [CI, 1.09 to 2.09] for studies with mean participant age <65 years and 1.05 [CI, 0.90 to 1.22] for studies with mean participant age > or =65 years). The RR was 1.18 (CI, 0.98 to 1.42) for cardiovascular mortality and 1.12 (CI, 0.99 to 1.26) for total mortality. For subclinical hyperthyroidism, the RR was 1.21 (CI, 0.88 to 1.68) for CHD, 1.19 (CI, 0.81 to 1.76) for cardiovascular mortality, and 1.12 (CI, 0.89 to 1.42) for total mortality (P for heterogeneity >0.50; I(2 )= 0% for all studies).
Individual studies adjusted for different potential confounders, and 1 study provided only unadjusted data. Publication bias or selective reporting of outcomes could not be excluded.
Subclinical hypothyroidism and hyperthyroidism may be associated with a modest increased risk for CHD and mortality, with lower risk estimates when pooling higher-quality studies and larger CIs for subclinical hyperthyroidism.
Annals of internal medicine 06/2008; 148(11):832-45. DOI:10.7326/0003-4819-148-11-200806030-00225 · 17.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To characterize the cardiovascular risk profile of subjects with high and normal-high concentrations of serum TSH in a sample of adult Spanish subjects from the island of Gran Canaria.
Cross-sectional population-based study.
After excluding 28 individuals on current treatment with levothyroxine and 9 others with TSH levels below the range of normality (0.3-4.9 mU/l), 704 randomly selected subjects (412 women; age range: 30-82 yr) belonging to the Telde Study were assessed.
Participants underwent physical examination and fasting blood analyses to determinate TSH, serum lipids, homocysteine, fibrinogen, von Willebrand factor, plasminogen activator inhibitor- 1, C-reactive protein, and insulin.
Twenty-nine participants had serum TSH concentrations above the normal range of normality. Among all the studied variables, only female sex and diastolic blood pressure were significantly associated with TSH levels > or =5 mU/l in a multivariate logistic regression analysis. If the upper normal limit of TSH was reduced up to 2.4 mU/l, an additional group of 106 subjects would be considered to have elevated TSH levels. A serum TSH > or =2.5 mU/l was positive and independently associated with female sex, body mass index, total cholesterol, and homocysteine, and negatively associated with smoking.
Although the impact of serum TSH levels on cardiovascular risk cannot be established from these findings, TSH values within the upper part of the usually accepted normal range were demonstrated to be associated with well-recognized risk factors for cardiovascular disease.
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