What to do with suspected congenital hypothyroidism?

From the Guidelines

For suspected congenital hypothyroidism, immediate referral to pediatric endocrinology and prompt initiation of levothyroxine (L-thyroxine) treatment is essential. This approach is crucial because thyroid hormones play a vital role in brain development and growth, and any delay in treatment can lead to permanent intellectual disability and other developmental issues 1. The importance of early identification and treatment is highlighted by the fact that congenital hypothyroidism can be identified through newborn screening, but acquired hypothyroidism and hyperthyroidism may present later in infancy or childhood with motor delays.

Key Considerations for Treatment

• Treatment should begin as soon as possible after diagnosis, ideally within the first two weeks of life.
• The starting dose of levothyroxine is typically 10-15 mcg/kg/day given once daily, aiming to normalize thyroid hormone levels rapidly.
• Regular monitoring of thyroid function tests (TSH and free T4) is necessary, initially every 1-2 weeks until levels normalize, then every 1-3 months during the first year of life, and less frequently thereafter.
• Medication administration should be consistent, preferably 30 minutes before feeding, and crushed and mixed with a small amount of breast milk, formula, or water.

Importance of Early Treatment

Early treatment is critical because thyroid hormones are essential for normal brain development, and delays in treatment can result in permanent intellectual disability and growth problems. Even a few weeks without adequate thyroid hormone during the neonatal period can have lasting neurodevelopmental consequences, as suggested by the potential for motor delays in conditions like cerebral palsy and the importance of early identification and evaluation 1.

Long-Term Management

Treatment is typically lifelong for permanent congenital hypothyroidism, though some transient forms may allow for a trial off medication after age three. Parents should be educated about the importance of consistent medication administration and regular follow-up to ensure the best possible outcomes for their child.

From the FDA Drug Label

Levothyroxine sodium is indicated in patients from birth to less than 17 years of age: • As a replacement therapy in primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism. Rapid restoration of normal serum T4 concentrations is essential for preventing the adverse effects of congenital hypothyroidism on cognitive development as well as on overall physical growth and maturation. Therefore, initiate levothyroxine sodium therapy immediately upon diagnosis.

Suspected Congenital Hypothyroidism should be treated with levothyroxine sodium therapy as soon as possible after diagnosis.

• The goal is to rapidly restore normal serum T4 concentrations to prevent adverse effects on cognitive development and physical growth and maturation.
• Levothyroxine sodium is generally continued for life in these patients 2.
• It is essential to closely monitor infants during the first 2 weeks of levothyroxine sodium therapy for cardiac overload and arrhythmias 2.

From the Research

Diagnosis and Screening

• Congenital hypothyroidism (CH) is a cause of preventable mental retardation, and timely diagnosis and treatment by the primary care physician is very important 3.
• Newborn screening (NBS) for CH should be performed in all infants, and prompt diagnosis by NBS leading to early and adequate treatment results in grossly normal neurocognitive outcomes in adulthood 4.
• NBS for CH should be performed between the second and fifth days of life with capillary blood done with a heel prick and must be confirmed by measurement of thyroid hormones in venous blood 3.

Treatment and Management

• The recommended initial treatment of CH is levothyroxine, 10 to 15 mcg/kg daily 4, 3.
• The goals of treatment are to maintain consistent euthyroidism with normal thyroid-stimulating hormone and with free thyroxine in the upper half of the age-specific reference range during the first 3 years of life 4.
• Treatment should not be delayed or suspended during the first 3 years of life due to the deleterious effect on neurodevelopment in case of low thyroid hormones during this time 3.
• Preterm or sick infants or those with Down syndrome require special consideration 3.

Special Considerations

• Controversy remains regarding the detection of thyroid dysfunction and optimal management of special populations, including preterm or low-birth-weight infants and infants with transient or mild CH, trisomy 21, or central hypothyroidism 4.
• Imaging studies for congenital hypothyroidism may be unlikely to change immediate management in the majority of cases, but can help establish an etiology for the condition, and in less-common causes of congenital hypothyroidism may have implications on treatment decisions, prognosis, and counseling 5.
• Physicians need to consider hypothyroidism in the face of clinical symptoms, even if NBS thyroid test results are normal, and measurement of serum thyroid-stimulating hormone and free thyroxine is indicated when clinical symptoms and signs of hypothyroidism are present 4.