Introduction: Significant changes in thyroid hormones occur during the first weeks after birth. We assessed the degree of changes in thyroid-stimulating hormone (TSH) and total thyroxin (T4) concentrations in neonates screened seven days after the first high serum TSH levels, just before starting treatment. Materials and Methods: This prospective study was carried out on newborns referred for their high TSH concentrations on heel blood spot in hypothyroidism screening tests (5-20 miu/ml), between December 2009 and December 2010. First, serum TSH and T4 were assessed by radioimmunoassay. One week later, in neonates with the first serum TSH≥10, serum TSH and T4 were rechecked before starting treatment. Any definite decision to continue treatment was based on the second test results. Results: The results showed a significant decrease in serum TSH level after one week (p<0.01). Serum T4 level increased significantly in neonates with the first serum TSH≥40 (p<0.05), while no significant difference was observed in other infants with the first serum TSH<40. Incidence rate of Congenital Hypothyroidism (CH) reduced from 1/329 to 1/851, during the study. Conclusions: It may be appropriate to repeat serum T4 and TSH concentrations after 2 and 4 weeks in neonates with normal serum T4 but elevated TSH. In the case of persistent TSH elevation, the infant should be treated as this can prevent unnecessary treatments, family stress and iatrogenic hyperthyroidism in these patients.