Improved diagnosis of mild hypothyroidism using time-of-day normal ranges for thyrotropin.

Abstract

OBJECTIVE:

To assess clinical utility of time-of-day-based thyrotropin (TSH) ranges.

STUDY DESIGN:

Ranges for TSH at 8 am, 4 pm, and am/pm TSH ratio were developed from prior data in 94 typical children (age, 5 to 18 years). Data for these values in 227 short children (1.5 to 18 years) were compared with those in typical children.

RESULTS:

Short children included idiopathic short stature (ISS, n=153), central hypothyroidism (Central, n=42), and mild primary hypothyroidism (Primary, n=32), referred for evaluation of growth. In typical children, ISS, and Primary, 8 am TSH was greater than 4 pm TSH (P<.05). In Primary, 8 am TSH was greater than normal. Only 4 with Primary had elevated 4 pm TSH (using usual laboratory range of 0.5 to 4 mU/L). In contrast, only 63% of 4 pm TSHs in Primary were elevated. compared with 95% confidence limits in typical children. In Central, 8 am TSH and 4 pm TSH were within normal time-of-day range, and FT4 was in lowest one-third of normal. am/pm TSH ratio was less than 95% confidence limits in 76% of those with Central.

CONCLUSIONS:

Either 8 am TSH or 4 pm TSH (compared with time-of-day normal range) can identify TSH elevation. Low am/pm TSH ratio (FT4 in lowest one-third of normal) confirms central hypothyroidism. Thus, time-of-day TSH ranges should be used for accurate diagnosis and more appropriate cost-effective treatment of mild hypothyroidism.

• Authors: Susan R Rose
• Journal: The Journal of pediatrics (J Pediatr) Vol. 157 Issue 4 Pg. 662-7; 667.e1 (Oct 2010) ISSN: 1097-6833 [Electronic] United States
• PMID: 20542290 (Publication Type: Journal Article)
• Copyright: Copyright (c) 2010 Mosby, Inc. All rights reserved.

Chemical References

• Thyrotropin
• Growth Hormone

Topics

• Adolescent
• Body Height
• Child
• Child, Preschool
• Cost-Benefit Analysis
• Female
• Growth Hormone (deficiency)
• Humans
• Hypothyroidism (blood, economics, therapy)
• Male
• Reference Values
• Severity of Illness Index
• Thyrotropin (blood)
• Time Factors
• Treatment Outcome