Serum TSH, T₄, and Thyroid Antibodies in the United States Population (1988 to 1994): National Health and Nutrition Examination Survey (NHANES III)

Abstract

NHANES III measured serum TSH, total serum T(4), antithyroperoxidase (TPOAb), and antithyroglobulin (TgAb) antibodies from a sample of 17,353 people aged > or =12 yr representing the geographic and ethnic distribution of the U.S. population. These data provide a reference for other studies of these analytes in the U.S. For the 16,533 people who did not report thyroid disease, goiter, or taking thyroid medications (disease-free population), we determined mean concentrations of TSH, T(4), TgAb, and TPOAb. A reference population of 13,344 people was selected from the disease-free population by excluding, in addition, those who were pregnant, taking androgens or estrogens, who had thyroid antibodies, or biochemical hypothyroidism or hyperthyroidism. The influence of demographics on TSH, T(4), and antibodies was examined. Hypothyroidism was found in 4.6% of the U.S. population (0.3% clinical and 4.3% subclinical) and hyperthyroidism in 1.3% (0.5% clinical and 0.7% subclinical). (Subclinical hypothyroidism is used in this paper to mean mild hypothyroidism, the term now preferred by the American Thyroid Association for the laboratory findings described.) For the disease-free population, mean serum TSH was 1.50 (95% confidence interval, 1.46-1.54) mIU/liter, was higher in females than males, and higher in white non-Hispanics (whites) [1.57 (1.52-1.62) mIU/liter] than black non-Hispanics (blacks) [1.18 (1.14-1.21) mIU/liter] (P < 0.001) or Mexican Americans [1.43 (1.40-1.46) mIU/liter] (P < 0.001). TgAb were positive in 10.4 +/- 0.5% and TPOAb, in 11.3 +/- 0.4%; positive antibodies were more prevalent in women than men, increased with age, and TPOAb were less prevalent in blacks (4.5 +/- 0.3%) than in whites (12.3 +/- 0.5%) (P < 0.001). TPOAb were significantly associated with hypo or hyperthyroidism, but TgAb were not. Using the reference population, geometric mean TSH was 1.40 +/- 0.02 mIU/liter and increased with age, and was significantly lower in blacks (1.18 +/- 0.02 mIU/liter) than whites (1.45 +/- 0.02 mIU/liter) (P < 0.001) and Mexican Americans (1.37 +/- 0.02 mIU/liter) (P < 0.001). Arithmetic mean total T(4) was 112.3 +/- 0.7 nmol/liter in the disease-free population and was consistently higher among Mexican Americans in all populations. In the reference population, mean total T(4) in Mexican Americans was (116.3 +/- 0.7 nmol/liter), significantly higher than whites (110.0 +/- 0.8 nmol/liter) or blacks (109.4 +/- 0.8 nmol/liter) (P < 0.0001). The difference persisted in all age groups. In summary, TSH and the prevalence of antithyroid antibodies are greater in females, increase with age, and are greater in whites and Mexican Americans than in blacks. TgAb alone in the absence of TPOAb is not significantly associated with thyroid disease. The lower prevalence of thyroid antibodies and lower TSH concentrations in blacks need more research to relate these findings to clinical status. A large proportion of the U.S. population unknowingly have laboratory evidence of thyroid disease, which supports the usefulness of ...

Prevalence of subclinical hypothyroidism in adults visiting primary health-care setting in Riyadh

“…These percentages are comparable with those reported in some other studies [9,13,15,22], yet are higher than those reported by others [8,23,24]. Estimates of subclinical hypothyroidism prevalence vary by the type of population accessed, i.e., sampled from community, hospital, nursing home or primary care, concurrent comorbidity and the TSH assay, and cut-off values used [25]. …”

“…The prevalence in women over age 80 years is lower, about 6% [25]. In our study, 15.4% of those 60 years and above had subclinical hypothyroidism, while only 9.9% of <60 years age had high TSH, and this was not statistically significant; however, mean TSH was significantly higher in elderly.…”

Lower levels of TSH are associated with a lower risk of papillary thyroid cancer in patients with thyroid nodular disease: thyroid autonomy may play a protective role

“…When patients were classified as affected by benign thyroid disease or PTC according to the results of cytology, the age-dependent reduction of TSH levels was highly significant in the first group, while in patients with PTC this phenomenon was much less evident. Indeed, the TSH levels in patients with PTC were close to the agespecific distribution of TSH found in people living in iodine sufficient areas, as reported in the NHANES III survey (Hollowell et al 2002, Aoki et al 2007, Surks & Hollowell 2007. These data strongly suggest that in our series of patients, the higher levels of TSH in PTC with respect to BTND are not due to an increase of thyrotropin in patients with thyroid cancer, but are mainly related to the reduction of serum TSH in patients with nodular goiter.…”

Usefulness of serum thyrotropin for risk prediction of differentiated thyroid cancers does not apply to microcarcinomas: results of 1,870 Chinese patients with thyroid nodules

“…We have no solid explanation for this inconsistency. Nevertheless, because women tend to have a higher TSH [32], one may anticipate women would be more susceptible to DTC if they are not over-represented in the subgroup undergoing surgery for benign conditions than men.…”