Colorado Thyroid Disease Prevalence Study

[Guest guest]

The Colorado Thyroid Disease Prevalence Study

Gay J. Canaris, MD, MSPH; Neil R. Manowitz, PhD; Gilbert Mayor, MD; E.

Chester Ridgway, MD

http://archinte.ama-assn.org/cgi/content/abstract/160/4/526

Arch Intern Med. 2000;160:526-534.

Context The prevalence of abnormal thyroid function in the United States

and the significance of thyroid dysfunction remain controversial. Systemic

effects of abnormal thyroid function have not been fully delineated,

particularly in cases of mild thyroid failure. Also, the relationship

between traditional hypothyroid symptoms and biochemical thyroid function is

unclear.

Objective To determine the prevalence of abnormal thyroid function and the

relationship between (1) abnormal thyroid function and lipid levels and (2)

abnormal thyroid function and symptoms using modern and sensitive thyroid

tests.

Design Cross-sectional study.

Participants Participants in a statewide health fair in Colorado, 1995 (N =

25,862).

Main Outcome Measures Serum thyrotropin (thyroid-stimulating hormone [TSH])

and total thyroxine (T4) concentrations, serum lipid levels, and responses

to a hypothyroid symptoms questionnaire.

Results The prevalence of elevated TSH levels (normal range, 0.3-5.1 mIU/L)

in this population was 9.5%, and the prevalence of decreased TSH levels was

2.2%. Forty percent of patients taking thyroid medications had abnormal TSH

levels. Lipid levels increased in a graded fashion as thyroid function

declined. Also, the mean total cholesterol and low-density lipoprotein

cholesterol levels of subjects with TSH values between 5.1 and 10 mIU/L were

significantly greater than the corresponding mean lipid levels in euthyroid

subjects. Symptoms were reported more often in hypothyroid vs euthyroid

individuals, but individual symptom sensitivities were low.

Conclusions The prevalence of abnormal biochemical thyroid function

reported here is substantial and confirms previous reports in smaller

populations. Among patients taking thyroid medication, only 60% were within

the normal range of TSH. Modest elevations of TSH corresponded to changes in

lipid levels that may affect cardiovascular health. Individual symptoms were

not very sensitive, but patients who report multiple thyroid symptoms

warrant serum thyroid testing. These results confirm that thyroid

dysfunction is common, may often go undetected, and may be associated with

adverse health outcomes that can be avoided by serum TSH measurement.

From the Division of General Internal Medicine, Department of Medicine,

University of Nebraska Medical Center, Omaha (Dr Canaris); Knoll Pharmaceutical

Co, Mt Olive, NJ (Drs Manowitz and Mayor); and the Division of Endocrinology,

Metabolism, and Diabetes, Department of Medicine, University of Colorado Health

Science Center, Denver (Dr Ridgway). Dr Mayor is currently with the Mayor Group

LLC, town, NJ.