Consequences of Untreated Hypothyroidism in Children
Untreated hypothyroidism in children can lead to severe and permanent intellectual disability, growth failure, and irreversible neurological damage, with congenital hypothyroidism being a preventable cause of mental retardation when diagnosed and treated early.
Neurological and Cognitive Consequences
Intellectual disability: Untreated congenital hypothyroidism leads to intellectual disabilities 1. Children with delayed treatment show a 5-10 point decline in IQ, even when eventually treated 2.
Cognitive development impairment: Deficits persist in visuospatial abilities, memory, and attention domains, which correlate with the severity of early hypothyroidism 2.
Congenital cretinism: Characterized by severe growth failure, mental retardation, and other neuropsychologic defects, especially when maternal hypothyroidism is due to iodine deficiency 3.
Language and speech delays: Children show delayed speech and language development, even with early treatment 2.
Physical Growth and Development Issues
Growth failure: Untreated hypothyroidism causes significant growth retardation and can lead to short stature 3.
Delayed bone maturation: Hypothyroidism affects bone development, potentially causing permanent skeletal abnormalities 4.
Delayed puberty: Longstanding hypothyroidism can result in delayed sexual maturation and development 3.
Metabolic and Systemic Effects
Myxedema: Advanced hypothyroidism progresses to myxedema, characterized by severe swelling, particularly of the face 3.
Cardiovascular complications: Untreated hypothyroidism can lead to heart failure and other cardiovascular issues 5.
Metabolic disturbances: Including insulin resistance, hyperglycemia in diabetic patients, and lipid abnormalities 5.
Critical Timing for Treatment
Window of opportunity: Treatment in the first several weeks of life for congenital hypothyroidism can result in nearly normal intelligence and growth 3.
Permanent effects: Even brief periods of thyroid hormone deficiency during critical brain development periods can cause irreversible neurocognitive deficits 2.
Severity correlation: The severity of intellectual impairment correlates with the duration and degree of thyroid hormone deficiency 2.
Screening and Treatment Approach
Universal newborn screening: All infants should undergo screening for congenital hypothyroidism 1.
Prompt treatment initiation: The recommended initial treatment is levothyroxine, 10-15 mcg/kg daily 1.
Treatment goals: Maintain normal TSH with free thyroxine in the upper half of the age-specific reference range during the first 3 years of life 1.
Ongoing monitoring: Regular TSH monitoring (every 6-8 weeks after initiating treatment or changing dose) is essential to avoid overtreatment or undertreatment 5.
Special Considerations
Clinical vigilance: Physicians need to consider hypothyroidism when clinical symptoms are present (large posterior fontanelle, large tongue, umbilical hernia, prolonged jaundice, constipation, lethargy, hypothermia), even if newborn screening results are normal 1.
High-risk populations: Special attention should be given to preterm infants, low-birth-weight infants, and those with trisomy 21, who may have different thyroid function patterns 1.
Global disparity: Seventy percent of neonates worldwide do not undergo newborn screening for hypothyroidism, putting them at risk for preventable intellectual disability 1.
Early diagnosis and adequate treatment of hypothyroidism in children are crucial to prevent these serious and often permanent consequences, with particular emphasis on the critical periods of brain development during early life.