Delayed onset congenital hypothyroidism in a patient with DUOX2 mutations and maternal iodine excess

Area of Science:

• Endocrinology
• Genetics
• Environmental Health

Background:

• Congenital hypothyroidism (CH) is a common endocrine disorder.
• Newborn screening diagnoses most CH cases, enabling early intervention and preventing intellectual disability.
• However, some CH cases present with delayed onset, evading newborn screening.

Observation:

• A patient presented with delayed-onset CH despite a negative newborn screening result.
• The patient had both a genetic defect (DUOX2 mutations) and in utero iodine excess (maternal seaweed consumption).
• Overt CH developed at 3 months, resolving by age 3 with thyroxine supplementation, indicating transient CH.

Findings:

• This case demonstrates a dual etiology for CH: a DUOX2 genetic mutation and environmental iodine excess.
• The combination of genetic predisposition and environmental factors masked CH during newborn screening.
• The patient experienced transient CH, emphasizing the phenotypic variability of genetic CH defects.

Implications:

• Environmental factors can significantly modify the phenotype of genetic CH, potentially leading to false-negative newborn screening results.
• This case underscores the importance of considering environmental exposures in diagnosing and managing CH.
• Further research is needed to understand the interplay between genetic and environmental factors in CH pathogenesis and screening accuracy.