Mild Hypothyroidism in Childhood

Who, When, and How Should Be Treated?

Maria Cristina Vigone; Donatella Capalbo; Giovanna Weber; Mariacarolina Salerno

Disclosures

J Endo Soc. 2018;2(9):1024-1039. 

In This Article

Abstract and Introduction

Abstract

Mild hypothyroidism, also known as subclinical hypothyroidism (SH), is biochemically defined as serum TSH levels above the upper limit of the reference range, in the presence of normal serum concentrations of total T4 and free T4 (FT4). In the neonatal period, mild hypothyroidism can be defined by the presence of a TSH value between 6 and 20 mIU/L and normal FT4 levels. After the neonatal period, SH can be defined mild if TSH ranges between 4.5 and 10 mIU/L. The management of mild hypothyroidism in childhood is challenging. The major concern is to establish whether this condition should always be considered an expression of mild thyroid dysfunction. Indeed, the effects of untreated mild hypothyroidism are still not completely defined. In the neonatal period, concern exists about neurocognitive outcome; in children, although there is no clear evidence of alterations in growth or neurocognitive development, subtle cardiovascular abnormalities have been documented. Therefore, there is still uncertainty about the need of treatment across all ages, and the management should be based on the age of the child, the etiology, and the degree of TSH elevation, as well as on other patient factors. This review updates current evidences on diagnosis and management of mild hypothyroidism in childhood.

Introduction

Mild hypothyroidism, also known as subclinical hypothyroidism (SH), is biochemically defined as serum TSH levels above the upper limit of the reference range, in the presence of normal serum concentrations of total T4 and free T4 (FT4).[1] In the neonatal period, mild hypothyroidism can be defined by the presence of a TSH value between 6 and 20 mIU/L and normal FT4 levels.[2] After the neonatal period, SH can be defined as mild (TSH 4.5 to 10 mIU/L) or severe (TSH >10 mIU/L).[3] Due to the wide variability of TSH concentrations among healthy individuals[4] and among different biochemical methods,[5] two independent TSH measurements above the upper limit of the reference range, in the presence of normal FT4 values, are needed to define persistent SH.[3] Recent data confirm systematic differences between the most common commercially available TSH immunoassays,[5] and disagreement has been observed in particular for the normal upper range.[6]

In adults, treatment with levothyroxine (L-T4) is recommended when serum TSH levels are >10 mIU/L for the increased risk of hypothyroid symptoms and cardiovascular events, whereas for patients who have TSH levels <10 mIU/L, the management is based on individual factors.[7]

Mild hypothyroidism in children differs from that in adults in both the etiology and the natural history. Moreover, although in childhood, overt hypothyroidism is known to severely affect growth and neurocognitive development, the effects of mild hypothyroidism are still not completely defined. Therefore, the management of this condition is challenging and is strictly related to the age of the patients, differing between neonates and children.

This review provides an update on the diagnosis and management of mild SH in childhood.

Comments

3090D553-9492-4563-8681-AD288FA52ACE

processing....