Frequency of Congenital Hypothyroidism and Radiographic Assessment of Knee Epiphysis in Newborn

Congenital hypothyroidism (CH) is the commonest preventable cause of mental retardation in newborn. It is more prevalent in endemic goiter regions like Bangladesh. The clinical manifestations are often subtle or absent at birth. As early clinical diagnosis is difficult without newborn screening, most cases of congenital hypothyroidism remain undetected before three months of age. Before the appearance of clinical manifestation, CH can be identified by a simple knee X-ray. This cross-sectional observational study was conducted in the department of pediatrics, Rajshahi Medical College Hospital, Bangladesh from January 2015 to December 2015, to compare between radiographic appearance of knee epiphysis and biochemical data as a screening tool for congenital hypothyroidism in neonate. Total 100 term neonates aged 7 days to 28 days admitted in the department of pediatrics, Rajshahi Medical College Hospital, Bangladesh were included in this study by purposive sampling method. Digital X-ray of knee joint was performed in all (100) cases. If the epiphysial diameter was between 0-8 mm then serum TSH and T₄ level was measured and compare the both results. Among the 100 X-rays of the knee, size of the epiphysis of 74 neonates was normal (>8 mm). Twenty six (26) neonates had epiphysial size between 0-8mm in diameter. Among these 26 neonates, both epiphysis (distal femoral and proximal tibial) were absent in 20(77.0%) neonates and 6 neonates had epiphysis size <8 mm in diameter. Out of these suspected 26 cases, two had TSH level <10 mIU/L but T₄ level was <6 μgm/dl and 3 other suspected patients had T₄ level more than 6μgm/dl but TSH level of those 3 patients were >10 mIU/L. These 5 cases are diagnosed as suspected hypothyroidism and advised for follow up. Rest of the neonates (21 cases) had both TSH level >10 mIU/L and T₄ level <6 μgm/dl. This study was found when either the individual epiphysial diameter or combined mean epiphysial size in diameter between 0-8 mm, we should strongly suspect congenital hypothyroidism and confirm it with biochemical data.