Prediction of Transient or Permanent Congenital Hypothyroidism

Abstract

Aim:Congenital hypothyroidism (CH) is one of the most common endocrinological problems in the neonatal period. CH, which occurs in 1:3,000-4,000 births, is a preventable cause of mental retardation. In the literature, the most common cause of CH is dysgenesis of the thyroid gland, followed by thyroid dyshormonogenesis. We aimed to determine the prevalence of permanent (P-CH) and transient (T-CH) CH in cases followed up with a diagnosis of CH and to identify a prediction method for persistency.Materials and Methods:We retrospectively analyzed the medical records of 105 children with CH. TSH levels in a screening program, TSH and fT4 levels of the first venous sample, 10-15th day of treatment, monthly in the first 6 months, 2-3 monthly until 18th months, and 6-monthly until 3 years of age were recorded. L-T4 doses (per microgram per body weight) in each visit were also recorded.Results:From the 105 children (58 males, 47 females) enrolled in this study, 38 (36.2 %) were referred from the National Newborn Screening Program. Treatment was discontinued during the 3rd year follow-up period in 44 (41.9 %) of the cases with normal thyroid gland morphology. L-thyroxine (L-T4) therapy was discontinued at a median age of 1.9+-1.08 years.TSH levels at the time of diagnosis were higher in the P-CH group, but this difference was not statistically significant (p=0.165). At the sixth month, first and second years of follow-up, L-T4 doses were significantly higher in the P-CH than in the T-CH group (p<0.001, p<0.001, p<0.001 respectively). TSH levels were also higher in the P-CH group than in the T-CH group (p=0.123, p=0.038, p=0.049 respectively). Consistent with these results, measured fT4 levels were found to be lower in the P-CH group compared to the T-CH group (p=0.431, p=0.361, p=0.028 respectively).Conclusion:L-T4 doses at 6, 12 and 24 months may predict transient hypothyroidism in patients with normal thyroid gland morphology before 36 months.

Keywords

• congenital hypothyroidism
• dyshormonogenesis
• screening
• thyroid dysgenesis
• permanent hypothyroidism
• transient hypothyroidism