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J Clin Endocrinol Metab. 2008 Apr;93(4):1224-30. doi: 10.1210/jc.2006-2300. Epub 2008 Jan 29.

Thyrotropin levels in a population with no clinical, autoantibody, or ultrasonographic evidence of thyroid disease: implications for the diagnosis of subclinical hypothyroidism.

Author information

1
Program in Epidermology, Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109-1024, USA. tehamilton@aol.com

Abstract

CONTEXT:

The current debate regarding whether to decrease the upper limit for the TSH reference range to 2.5 microIU/ml has considerable potential impact on the diagnosis and treatment of subclinical hypothyroidism worldwide.

OBJECTIVE:

We report an analysis of TSH distribution in a population with no evidence of thyroid disease, including a normal thyroid ultrasound.

DESIGN:

A subset of the Hanford Thyroid Disease Study cohort was used to examine the TSH distribution in a population having no evidence of thyroid disease, seronegative thyroid autoantibodies, no history of thyroid medications, and a normal thyroid ultrasound. The shape of the TSH distribution was compared with the Gaussian and lognormal distributions.

SETTING:

This study was performed in the general community.

PARTICIPANTS:

Of 1861 Hanford Thyroid Disease Study participants with TSH measured by ELISA who also had thyroid peroxidase antibody measurements, 766 comprised the normal reference group 3 (NRG-3) with no evidence of thyroid disease, including no positive antibodies and normal thyroid ultrasound.

MAIN OUTCOME MEASURE:

TSH was measured.

RESULTS:

The TSH distribution in the NRG (NRG-3) was right skewed and followed an approximate lognormal distribution. The best estimates of the 97.5th percentile, the percentage above 2.5 microIU/ml, and the percentage above 3.0 microIU/ml for TSH by 3rd generation immunochemiluminometric assay are 4.1 microIU/ml, 20% and 10.2%, respectively.

CONCLUSION:

These results indicate that the TSH reference range should be narrowed and support a value of approximately 4.0 as the upper-reference limit.

Comment in

PMID:
18230665
PMCID:
PMC2729186
DOI:
10.1210/jc.2006-2300
[Indexed for MEDLINE]
Free PMC Article

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