Long term follow-up of the patients with delayed TSH elevation or subclinical hypothyroidism has been seldom reported. The purpose of this study was to explore the diagnostic criteria for subclinical hypothyroidism and the initial dosage of L-thyroxine through long-term follow up for infants with subclinical hypothyroidism ，and evaluate the curative effect.

Study Type: Observational

Study Design: Screening, Longitudinal, Defined Population, Prospective Study

Long term follow-up of the patients with delayed TSH elevation or subclinical hypothyroidism has been seldom reported. The purpose of this study was to explore the diagnostic criteria for subclinical hypothyroidism and the initial dosage of L-thyroxine through long-term follow up for infants with hyperthyrotropinemia，and evaluate the curative effect.All live-born neonates in province took part in the screening program from October, 1999 to September ,2006. Laboratory tests are performed as a time resolved fluoro-immunoassay (TRFIA). TSH is measured with a cut-off > 9 mU/L. The diagnostic standard for subclinical hypothyroidism was:

TSH ≥ 20 mU/L, T3 and T4 normal or low-normal ,or TSH > 5.6 mU/L and < 20 mU/L on initial determination and on follow-up or TSH levels increase on follow-up and/or gradually declining T4 levels.L-Thyroxine was administered for substitution therapy. After 2 years therapy，allround evaluation was performed. Compare the correlation to effects with different level of TSH、starting time of therapy and environment. Compare the effects between subclinical、temporary and permanent hypothyroidism.

Inclusion Criteria:

• The diagnostic standard for manifest hypothyroidism and subclinical hypothyroidism was defined as follows:
• Hypothyroidism - TSH > 40 mU/L and T3 and T4 below the reference range or TSH >
• 40 mU/L, T3 normal and T4 below the reference range [2]
• Subclinical hypothyroidism - TSH ≥ 20 mU/L, T3 and T4 normal or low-normal or TSH
• > 5.6 mU/L and < 20 mU/L on initial determination and on follow-up or TSH levels increase on follow-up and/or gradually declining T4 levels.

Gender Eligibility for this Clinical Trial: Both

Minimum Age for this Clinical Trial: N/A

Maximum Age for this Clinical Trial: 5 Years

Lead Sponsor: Zhejiang University

Overall Clinical Trial Officials and Contacts

zhengyan Zhao, doctor Study Director Pediatric Society of the Chinese Medical Association  

Information obtained from ClinicalTrials.gov on August 29, 2008

Link to the current ClinicalTrials.gov record. http://clinicaltrials.gov/show/NCT00497575

Study ID Number: no. 2002C23037

ClinicalTrials.gov Identifier: NCT00497575

Health Authority: China: Ministry of Health