| Abstract |
BACKGROUND: Overt hypothyroidism has been found to be associated with
cardiovascular disease. Whether subclinical hypothyroidism and thyroid
autoimmunity are also risk factors for cardiovascular disease is
controversial. OBJECTIVE: To investigate whether subclinical
hypothyroidism and thyroid autoimmunity are associated with aortic
atherosclerosis and myocardial infarction in postmenopausal women. DESIGN:
Population-based cross-sectional study. SETTING: A district of Rotterdam,
The Netherlands. PARTICIPANTS: Random sample of 1149 women (mean age +/-
SD, 69.0 +/- 7.5 years) participating in the Rotterdam Study.
MEASUREMENTS: Data on thyroid status, aortic atherosclerosis, and history
of myocardial infarction were obtained at baseline. Subclinical
hypothyroidism was defined as an elevated thyroid-stimulating hormone
level (>4.0 mU/L) and a normal serum free thyroxine level (11 to 25 pmol/L
[0.9 to 1.9 ng/dL]). In tests for antibodies to thyroid peroxidase, a
serum level greater than 10 IU/mL was considered a positive result.
RESULTS: Subclinical hypothyroidism was present in 10.8% of participants
and was associated with a greater age-adjusted prevalence of aortic
atherosclerosis (odds ratio, 1.7 [95% CI, 1.1 to 2.6]) and myocardial
infarction (odds ratio, 2.3 [CI, 1.3 to 4.0]). Additional adjustment for
body mass index, total and high-density lipoprotein cholesterol level,
blood pressure, and smoking status, as well as exclusion of women who took
beta-blockers, did not affect these estimates. Associations were slightly
stronger in women who had subclinical hypothyroidism and antibodies to
thyroid peroxidase (odds ratio for aortic atherosclerosis, 1.9 [CI, 1.1 to
3.6]; odds ratio for myocardial infarction, 3.1 [CI, 1.5 to 6.3]). No
association was found between thyroid autoimmunity itself and
cardiovascular disease. The population attributable risk percentage for
subclinical hypothyroidism associated with myocardial infarction was
within the range of that for known major risk factors for cardiovascular
disease. CONCLUSION: Subclinical hypothyroidism is a strong indicator of
risk for atherosclerosis and myocardial infarction in elderly women. |