Abstract

Objective: In this study, we aimed to determine the frequency and etiology of transient and permanent congenital hypothyroidism (CH), and to investigate the role of laboratory data in predicting permanent and transient hypothyroidism.

Method: A total of 217 patients (111 girls, 106 boys) on L-thyroxine (LT4) therapy who were diagnosed with CH and followed up for at least 3 years were included in the study. The files of the patients were scanned retrospectively. Thyroid stimulating hormone (TSH), free thyroxine (fT4) levels, thyroid ultrasonography results and treatment doses were noted at the time of diagnosis and 4-6 weeks after treatment was discontinued.

Results: Permanent CH was found in 59%, and transient CH in 41% of the cases. The most common causes of permanent, and transient CH were dysgenesis (77.3%), and dyshormonogenesis or unexplained etiology (51.6%), respectively. TSH level at the time of diagnosis was found to be statistically significantly higher in the permanent group, while fT4 levels at the 3rd year were significantly higher in patients with transient CH (p<0.0001, and p=0.002, respectively). LT4 doses were significantly lower in the transient CH group (p<0.0001).

Conclusion: Most frequently permanent hypothyroidism due to dysgenesis was detected. It has been shown that high TSH levels at the time of diagnosis, low fT4 levels in the 3rd year of treatment, and LT4 doses at the time of treatment discontinuation are determinative factors in the differential diagnosis made between permanent and transient CH.