Prevalence and relevance of thyroid dysfunction in 1922 cholesterol screening participants

Controversy persists about the role of subclinical hypothyroidism in hyperc holesterolemia. This study aimed to assess in a clinically healthy, middle- aged population of employees the prevalence of thyroid function disorders a nd their relation to demographic variables and cardiovascular risk factors. 1922 (former) employees were screened with follow-up of newly identified c ases of undiagnosed (subclinical) hypothyroidism and hyperthyroidism. Thyro id stimulating hormone (TSH), prevalence and course of (subclinical) hypo- and hyperthyroidism and their relation to cardiovascular risk factors (chol esterol, low-density lipoprotein cholesterol, high-density lipoprotein chol esterol, triglycerides, smoking, systolic and diastolic blood pressure) wer e assessed. The prevalence of newly diagnosed subclinical hypothyroidism (c ut-off TSH concentration: 4.0 mU/L) was 1.1% (17 women and 5 men) with a me an TSH concentration of 7.37 (95 % CI 5.18-9.56) mU/L. No case of overt hyp othyroidism could be diagnosed. Elevated levels of antibodies to microsomal or thyroglobulin antigens were detected in six subjects with subclinical h ypothyroidism (27.3%). Fifteen subjects (0.8%, 13 women and 2 men) had TSH concentrations below 0.1 mU/L. The cardiovascular risk profile of subjects with mild subclinical hypothyroidism was not different from subjects with n ormal TSH levels. The prevalence of subclinical hypothyroidism was 0.8% in normocholesterolemic (cholesterol <5.2 mmol/l) and 1.4% in hypercholesterol emic subjects (n.s.). One woman each with the subclinical form of the disea se developed hypothyroidism or hyperthyroidism after 21 and 11 months of fo llow-up, respectively. Subclinical hypothyroidism and subclinical hyperthyr oidism were rarely observed in a target group for coronary heart disease pr evention. Mild subclinical hypothyroidism was not associated with any adver se cardiovascular risk profile. These results argue against indiscriminate measurements of TSH concentrations in clinically healthy subjects either wi th normocholesterolemia or hypercholesterolemia. (C) 2000 Elsevier Science Inc. All rights reserved.