RESEARCH - Natural history of thyroid function tests over 5 years in a large pediatric cohort

October 21, 2009

J Clin Endocrinol Metab. 2009 May;94(5):1678-82. Epub 2009 Feb 24.

Natural history of thyroid function tests over 5 years in a large

pediatric cohort.

Lazar L, Frumkin RB, Battat E, Lebenthal Y, M, Meyerovitch J.

The Z. and Sara Lea Shafer Institute for Endocrinology and

Diabetes, National Center for Childhood Diabetes, Schneider Children's

Medical Center of Israel, Petah Tikva 49202, Israel.

CONTEXT: Because clinical manifestations of thyroid disorders are

variable and subtle in children and adolescents, thyroid function

tests are often repeated in patients with nonspecific symptoms.

OBJECTIVES: The objective of the study was to determine the natural

history of initial abnormal TSH and define populations at greater risk

for developing a subsequent thyroid dysfunction.

METHODS: A total of 121,052 of 1.043 million outpatients aged 0.5-16

yr insured by the Clalit Health Medical Organization had a TSH

determination in 2002 and follow-up to 2007. Extracted from the Clalit

Health Medical Organization database were their demographic data,

referral diagnoses, and laboratory results (TSH, free T(4), thyroid

antibodies). Excluded were patients with overt hypothyroidism or

hyperthyroidism on initial testing.

RESULTS: Results of 96.5% of initial serum TSH concentrations were

normal (0.35-5.5 mIU/liter), 0.2% were low (<0.35 mIU/liter), 2.9%

elevated (>5.5 to <or=10 mIU/liter), and 0.4% highly elevated (>10

mIU/liter). The frequency of TSH testing increased with age and female

gender. During follow-up, repeated (two to more than four) TSH tests

were performed in 45.7% of the patients. In the second TSH

determination, normal TSH was documented in 40, 73.6, and 78.9% of

those whose initial serum TSH was highly elevated, elevated, and low,

respectively, and in 97% of those with normal initial TSH. Predictive

factors for a sustained highly elevated TSH were initial TSH greater

than 7.5 mIU/liter (P = 0.014) and female gender (P = 0.047).

CONCLUSIONS: In the pediatric population, initial normal or slightly

elevated TSH levels are likely to remain normal or spontaneously

normalize without treatment. Patients with initial levels greater than

7.5 mIU/liter, particularly girls, are at a greater risk for sustained

abnormal TSH levels.

PMID: 19240148

Not an MD

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