ESPE Abstracts

Background and Aim: Congenital hypothyroidism (CH) is a well-known condition. Nevertheless, recent questions in clinical practice, especially in neonatal intensive care setting, prompted us to review the natural history of CH in our cohort.

Methods: This is a retrospective, observational study collecting anamnestic, anthropometric (height SDS, BMI SDS), diagnostic (TSH, fT4, thyroid ultrasound) and therapeutic data (dose of levothyroxine) in all children diagnosed of CH through national screening from January 2000 to July 2020 at our paediatric department. Data were collected at birth (T0), at 3 years old (T1), at onset of puberty (T2) and at final height (T3). Enrolled patients were retrospectively classified in persistent CH (pCH) or transient CH (tCH) according to clinical and biochemical subsequent trend. Statistical analysis was carried out on STATISTICA (StatSoft Inc, Tulsa, OK, USA) through Mann-Whitney U and Friedman ANOVA tests.

Results: Among 78 enrolled patients (51% females, 71% Caucasian), CH was permanent in 73% (9% thyroid agenesis, 19% ectopic gland, 9% hypoplastic gland, 63% gland in situ). At diagnosis, biochemical and therapeutic features were more severe in pCH than in tCH (initial TSH 126.18±181.68 vs. 43.25±29.57 μIU/ml, p 0.04; starting levothyroxine dose 8.62±8.80 vs. 5.73±2.52 mcgr/kg/die, p 0.04). Longitudinal analysis documented normal growth in pCH along follow-up (height SDS: T0 0.25 ± 1.39, T1 -0.35 ± 1.06, T2 0.10 ± 1.23, T3 -0.05 ±1.20, p 0.82, χ² 0.90). In pHC, 10.5% was preterm, while this rate increased to 28.6% in tCH group (p 0.04). In pHC, at birth, preterm babies showed lower levels of TSH than ones at term (34.85±20.86 vs. 131.08±191.73 μIU/ml, p 0.04), an increased rate of gland abnormalities (50% vs. 29%) and the need of higher initial dose of levothyroxine (14.75±24.29 vs. 6.83±3.78 mcgr/kg/die, p 0.04).

Conclusions: Our data confirm the increase of pCH with in situ gland than historically described and that an appropriate therapy ensures long-term normal growth. At birth, TSH levels and the initial dose of levothyroxine seem to predict pCH. Nevertheless, considering the increasing number of preterm births, our data underline the need to better describe pCH in this category of patients, taking into consideration their immaturity of both hypothalamic-pituitary-thyroid axis and biosynthetic functions, their nutritional deficiencies and increased tissue metabolism and the potential effect of concomitant therapies.