Thyroid functions and serum lipids in older women: a population-based study

Abstract

Purpose: To determine if thyroid hormone deficiency, manifested by elevated serum thyrotropin (TSH), is associated with alterations in serum lipids in an unselected population of older women.

Subjects and methods: Population-based sampling of 279 ambulatory white women over age 65 studied at four US clinical centers, randomly selected from a cohort of 9,704 participants enrolled in the Study of Osteoporotic Fractures. A third-generation chemiluminescent TSH assay and serum lipid levels--total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides--were measured on fasting sera collected at the baseline visit. The cross-sectional relationships between TSH and lipid levels were analyzed.

Results: TSH was high (>5.5 mU/L) in 19 women (6.8%), and was low (< or =0.1 mU/L) in 10 (3.6%). After multiple adjustment, LDL-C was 17 mg/dL or 13% higher (95% confidence interval [CI] 1%, 25%), and HDL-C was 6.5 mg/dL or 12% lower (CI -0.2%, -25%) in women with high TSH compared with those with normal TSH. The ratio of LDL-C to HDL-C was 29% greater (CI 4%, 53%) among women with elevated TSH. Although total cholesterol was 8% higher among women with high TSH, this difference was not statistically significant (CI -1%, 15%). High TSH was found in 12% of the women with the combination of high cholesterol (>240 mg/dL), high LDL-C (>160 mg/dL), and low HDL-C (<45 mg/dL); likelihood ratio = 1.8) whereas high TSH was found in only 2.2% of women with normal lipids (likelihood ratio = 0.3).

Conclusion: Among older white women, high TSH is associated with deleterious changes in serum lipids, particularly HDL-C, LDL-C, and the ratio of LDL-C to HDL-C cholesterol. Women with multiple lipid abnormalities are twice as likely to have an increased TSH.