ESPE Abstracts

Objective: The incidence of congenital hypothyroidism (CH) has increased worldwide. Lowering cut-off in screening programs has led to an increase in the rate of transient CH. We aimed to evaluate the rates of permanent and transient CH in cases referred from the screening program and to investigate the clinical and laboratory factors to predict the transient CH.

Methods: 109 cases referred from the screening program to our hospital, from September 2015 to April 2018, and 52 cases were diagnosed with CH. Those cases were prospectively evaluated and cases completed regular 3-years-follow up (n=44) were re-investigated to determine the rates of permanent and transient CH.

Results: Fifteen cases (34%) were diagnosed with permanent CH and 29 cases (66%) were diagnosed with transient CH. Gestational age in weeks (w) and birth weight were 38.2 ± 1.31 and 3021.3 ± 389.6 gram (g) in the transient CH group and both were significantly lower compared to permanent CH cases with the results of 39.06 ± 1.33 w and 3375,3 ± 425,3 g (P=0.025, P=0.007). Transient CH rate was found to be 50 % (all hypoplastic) in the dysgenesis group and 73.3% together in groups with the normal and hyperplasic thyroid gland. While fT4, thyroid-stimulating hormone, and thyroglobulin levels at diagnosis do not predict transient/permanent CH, levothyroxine (LT-4) dosage was significantly lower in the transient CH group in all years. The optimal cut-off value with highest sensitivity and specificity for LT-4 dosage as a predictive marker to differentiate transient CH from permanent CH was found 2.27 µg/kg/day (P=0.004; sensitivity: 71%, specificity: 83%) at 1st year, 1.85 µg /kg/day (P=0.013; sensitivity: 66%, specificity: 72%) at 2nd year and 1.69 µg /kg/day at 3rd year (P<0.0001; sensitivity: 90%, specificity: 83%).

Conclusion: Transient CH is more frequent than expected. Our results suggest that the LT-4 requirement may be a good marker for predicting transient CH. Therefore, infants with CH requiring LT-4 doses <2.27 μg/kg/day at 1st year, <1.85 μg /kg/day at 2nd year may be re-evaluated earlier to discriminate transient CH.