ESPE Abstracts

Introduction: An increase in the incidence of congenital hypothyroidism (CH) with eutopic gland has been reported worldwide due to neonatal screening programs. Several studies have recently reported factors useful for predicting permanent CH (P-CH).

Objectives: To determine predictive factors that could distinguish between permanent and transient CH (T-CH) in patients with eutopic thyroid gland and normal neonatal screening.

Material and Methods: We conducted a retrospective study of patients diagnosed before 3 years of age with non-autoimmune CH and eutopic thyroid gland, born between 2002 and 2017. All patients were reevaluated from the age of 3, with TSH (µU/ml), T4L (ng/dl) (chemiluminescence), thyroid autoimmunity (anti-TPO and anti-TG), thyroid ultrasound and thyroid scintigraphy (I123). TSH>10 µU/ml was considered for initiation of treatment. Exclusion criteria: gestational age <37 weeks, birth weight <1500g, congenital heart disease, Down syndrome, surgery, or admission to the NICU. Variables analyzed were initial and reevaluation TSH and T4L levels, maximum dose of levothyroxine required, family history of thyroid disease, twin gestation, in vitro fertilization, intrauterine growth restriction, age at the first consultation, and age at initiation of replacement therapy. Statistical analysis was performed using SPSS.21. Considered statistically significant P<0.05.

Results: We included 47 patients of which 55.3% were male and diagnosed at a mean age of 12.10 months (SD: 10.16). After reevaluation, 27 patients (57.4%) required restarting levothyroxine treatment and were diagnosed of P-CH. The mean age at diagnosis was earlier in this group (mean: 10.40 months; SD: 8.91) (P=0.009). We found higher initial TSH levels in P-CH (mean: 12.72 µU/ml; SD: 4.24) compared to T-CH (mean: 10.64 µU/ml; SD: 1.87) (P=0.02). We observed a trend toward a higher levothyroxine dose requirement in patients with P-CH (median: 3.00 µg/kg/day; IC range: 1.00) compared to those with T-CH (median: 2.50 µg/kg/day; IC range: 0.50) (P=0.06). We did not identify any differences in T4L levels at the beginning or throughout the follow-up process. Moreover, 60.0% of patients with a personal history of twin gestation were diagnosed with P-CH. Similarly, 65.5% of P-CH had a family history of hypothyroidism, mainly maternal. However, sex, history of intrauterine growth restriction, or in vitro fertilization did not present any differences.

Conclusions: An earlier age of onset, higher TSH levels at diagnosis, higher levothyroxine requirements, family history of thyroid disease, and twin gestations may help predict P-CH in patients with eutopic thyroid glands.