Thyrotropin levels and their relationship with cardiovascular risk factors in the island of Gran Canaria, Spain. Implications of lowering the upper reference limit of thyrotropin stimulating hormone

Objective : 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. Design : Cross-sectional population-based study. Subjects : 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. Measurements : 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. Results : 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 >-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>-2.5 mU/l was positive and independently associated with female sex, body mass index, total cholesterol, and homocysteine, and negatively associated with smoking. Conclusions : 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.