Prediction of Transient or Permanent Congenital Hypothyroidism

INTRODUCTION: 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) / transient (T-CH) CH in cases followed up with a diagnosis of CH and identify a prediction method for persistency.
METHODS: We retrospectively analyzed medical records of 105 children with CH.
RESULTS: From the 105 children (58 males, 47 females) enrolled in this study, 38 (36.2 %) were referred from National Newborn Screening Program. Cases with normal thyroid appearance were evaluated as thyroid dyshormonogenesis (n: 94; 89.5 %), and other cases were evaluated as thyroid dysgenesis (n: 11; 10.5 %). 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.
At the time of diagnoses, fT4 level was significantly higher in T-CH group than P-CH including thyroid dysgenesis (p=0.037). 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 P-CH than T-CH group (p<0.001, p<0.001, p<0.001 respectively). TSH levels were also higher in P-CH than 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).

DISCUSSION AND CONCLUSION: L-T4 doses at 6, 12 and 24 months may predict transient hypothyroidism in patients with normal thyroid gland morphology before 36 months.