hypothyroidism%20(pediatric)
HYPOTHYROIDISM (PEDIATRIC)
Hypothyroidism is due to decreased or absent production of thyroid hormone.
Primary hypothyroidism is caused by generalized tissue resistance to thyroid hormone and disorders that affect the thyroid gland directly. It is responsible for majority of hypothyroid cases.
Central hypothyroidism is caused by hypothalamic or pituitary disorders.

Hypothyroidism%20(pediatric) Diagnosis

Classification

Differentiating Between Primary, Central and Subclinical Hypothyroidism

  • Overt primary hypothyroidism: Low free thyroxine (FT4) and elevated serum thyroid-stimulating hormone (TSH)
  • Subclinical primary hypothyroidism: Elevated TSH and normal FT4
    • Repeat thyroid function test should be done after 3-6 months to confirm the diagnosis
  • Central hypothyroidism: Low FT4 and low, normal or mildly elevated serum TSH

History

  • Prolonged gestation
  • Maternal history of thyroiditis (transient neonatal hypothyroidism)
  • Maternal exposure to radioiodine or intake of goitrogens (eg Amiodarone, antithyroid drugs)
  • Family history of hypothyroidism
  • Thyroid treatment for hyperthyroidism (eg Thionamides, radioiodine or surgery)
  • Viral infection followed by a painful thyroid gland with signs and symptoms of hyperthyroidism, later on manifesting signs and symptoms of hypothyroidism (subacute thyroiditis)
  • Iodine sources (Iodine deficiency/endemic goiter)
  • Excessive iodide intake (eg Kelps, radiocontrast dyes)
  • Intake of goitrogens (eg Lithium, Amiodarone, thionamides)
  • Head and neck radiation

Laboratory Tests

  • Patient’s age must be considered in the interpretation of thyroid function results

Confirmation of Hypothyroidism

  • Serum thyroid-stimulating hormone (TSH): Most valuable test for detecting hypothyroidism
  • Free thyroxine (FT4) levels also useful for confirmation
  • TSH and FT4 concentrations are higher in children, especially in the 1st week of life and throughout the 1st year

Other Thyroid Tests

  • Thyroid autoantibodies: Antithyroid peroxidase and antithyroglobulin autoantibodies
  • Thyroid scan, ultrasound
  • Fine needle aspiration (FNA): Recommended for all palpable solitary or dominant nodules, independent of size
    • FNA is preferred over thyroid scan or ultrasonography as the initial diagnostic test for thyroid nodules, although a previous ultrasound may aid the physician in performing the aspiration

Evaluation

Acquired Hypothyroidism

  • If suspected, the entire function of the hypothalamic-pituitary axis should be evaluated with appropriate tests
    • Once confirmed imaging studies of the brain and pituitary gland should be performed

Congenital Hypothyroidism

  • Most infants appear unaffected at birth; signs and symptoms may be delayed until 6-12 weeks of age or older
  • Newborn screening for congenital hyperthyroidism is crucial for early detection and treatment
    • Delaying treatment after 6 weeks of life is associated with increased risk of delayed cognitive development
    • Abnormal laboratory results must be communicated immediately so that empirical thyroid hormone replacement can be initiated even while waiting for confirmatory studies

Imaging

  • Cranial imaging such as magnetic resonance imaging (MRI) is recommended in patients with confirmed central hypothyroidism
Congenital Hypothyroidism
  • Present or absent femoral/tibial epiphyses in radiographic imaging of the knee may help assess the severity of intrauterine hypothyroidism
  • Scintigraphy and ultrasonography may also be used to assess the patient’s thyroid function and cause of the disease
    • Performing both scintigraphy and ultrasound is highly suggested in neonates with high thyroid-stimulating hormone (TSH) levels

Screening

Newborn Screening for Congenital Hypothyroidism

  • Goals of screening: To identify and treat patients at risk for the health consequences of thyroid dysfunction before they become clinically apparent
  • Additional indications and ideal time for screening:
    • Normal hospital delivery at term: 2-4 days of age
    • Infants in neonatal intensive care units (NICU), preterm babies, home births: Within 7 days of age
    • Maternal history of thyroid medication or family history of congenital hypothyroidism: Cord blood for screening

Types of Newborn Screening

  • Primary thyroid-stimulating hormone (TSH), backup free thyroxine (FT4): May miss thyroid-binding globulin deficiency, central hypothyroidism, hypothyroxinemia with delayed TSH elevation
  • Primary T4, backup TSH: May miss delayed TSH elevation with initial normal T4
  • Primary T4 and TSH: Ideal screening approach

Interpretation of Newborn Screening Results

  • Elevated TSH and low T4: Congenital hypothyroidism
  • Normal TSH and low T4: Transient hypothyroxinemia, central hypothyroidism, thyroid-binding globulin deficiency, isolated low T4
  • Elevated TSH and normal T4: Transient/permanent mild congenital hypothyroidism, delayed maturation of hypothalamic/pituitary axis, thyroid hormone resistance, Down syndrome, subclinical hypothyroidism
  • Delayed TSH elevation and low T4: Low or very low-birth weight infants, preterm infants, sick term newborn

Confirmation of Results

  • Infants with abnormal or borderline screening results should have free T4 and TSH drawn for definitive testing
    • Thyroid hormone replacement may be empirically initiated while awaiting confirmatory results

Secondary Screening for Congenital Hypothyroidism

Recommended for the following:

  • Preterm neonates
  • Infants with low-birth weight (LBW)
  • Infants with very low-birth weight (VLBW)
  • Unhealthy infants/preterm neonates previously admitted in the NICU
  • Newborn screening done within 1st 24 hours after birth
  • Multiple pregnancy
Digital Edition
Asia's trusted medical magazine for healthcare professionals. Get your MIMS JPOG - Malaysia digital copy today!
Sign In To Download
Editor's Recommendations
Most Read Articles
Pearl Toh, 2 days ago
Antiviral treatment with tenofovir alafenamide fumarate (TAF) during pregnancy in highly viraemic mothers effectively prevents mother-to-child transmission (MTCT) of hepatitis B virus (HBV) with no safety concerns, according to two studies presented during the AASLD 2020 Liver Meeting.