The prevalence of subclinical hypothyroidism at different total plasma cholesterol levels in middle aged men and women: a need for case-finding?

Clin Endocrinol (Oxf). 1999 Feb;50(2):217-20. doi: 10.1046/j.1365-2265.1999.00638.x.


Objective: In order to determine whether screening of thyroid function is justified in patients with hypercholesterolaemia, we determined the prevalence of subclinical hypothyroidism at different levels of total plasma cholesterol in middle-aged men and women.

Design and methods: 1200 participants were selected from a population based cross sectional study on risk factors for cardiovascular diseases. The participants were divided into three groups: total plasma cholesterol < 5 mmol/l, total plasma cholesterol 5-8 mmol/l, total plasma cholesterol > 8 mmol/l. Each group was comparable in size and sex distribution. Subclinical hypothyroidism was defined as plasma TSH levels higher than 4 mU/l, in the presence of normal free thyroxine (FT4(4)) concentration.

Results: Plasma samples of a total of 1191 participants were analyzed. The overall prevalence of subclinical hypothyroidism was 1.9% in men and 7.6% in women of middle age. In women the prevalence of subclinical hypothyroidism increased from 4.0 percent in the lowest, to 10.3 percent in the highest cholesterol stratum (P = 0.02). In men, the mean prevalence was 1.8 percent and roughly similar in the various strata. After age correction, an increase of 1 mU/l TSH in women was associated with an increase of 0.09 mmol/l total plasma cholesterol (95% confidence interval (CI) 0.02-0.16 mmol/l). A similar trend was found in men (0.16 mmol/l, 95% CI -0.02-0.34 mmol/l).

Conclusions: In the population, the prevalence of subclinical hypothyroidism is up to 10 percent in middle aged women with high levels of total plasma cholesterol and may justify case-finding. In these women approximately 0.5 mmol/l of total plasma cholesterol can be attributed to the subclinical thyroid dysfunction. In men a similar correlation between thyroid dysfunction and total plasma cholesterol is seen, but the prevalence of thyroid dysfunction is considerably lower.

MeSH terms

  • Cholesterol / blood*
  • Confidence Intervals
  • Female
  • Humans
  • Hypothyroidism / blood*
  • Hypothyroidism / diagnosis
  • Hypothyroidism / epidemiology*
  • Male
  • Mass Screening
  • Middle Aged
  • Prevalence
  • Sex Distribution
  • Thyrotropin / blood


  • Thyrotropin
  • Cholesterol