Abstract
Congenital hypothyroidism (CH) is one of the major preventable causes of intellectual disability. This study evaluates the incidence of CH through a newborn screening (NBS) program in eastern Morocco. A descriptive cross-sectional design was used and heel prick blood samples were collected on blotting paper to measure Thyroid-Stimulating Hormone (TSH) using an immunofluorimetric assay. 4062 newborns were screened (51.3% male, 48.7% female). TSH levels significantly varied by age: newborns sampled before 24 h had a higher median TSH (3.7 µU/mL [0.10-28.90]) compared to those sampled at 24 h or more (2.1 µU/mL [0.10-32.30]; p < 0.001). Using age-specific cut-off values, 18 suspected CH cases were recalled (recall rate: 0.44%). Among the 16 cases who completed confirmatory testing, 4 had transient hyperthyrotropinemia (HTT), characterized by mildly abnormal serum TSH and T4 levels that normalized spontaneously after few months without treatment. Three cases were diagnosed with CH confirmed at birth with markedly elevated serum TSH concentrations and significantly reduced T4 levels. Consequently, the birth prevalence of CH confirmed at birth was 1:1354 live births. The median preanalytical delay was 6 days (IQR: 3-12) and the TSH result turnaround was 8 days (IQR: 5-15), potentially affecting timely intervention. This first report from eastern Morocco confirms the relevance of neonatal screening but highlights delays that must be addressed to enhance early diagnosis and management.