ESPE Abstracts

Background: A second screening for congenital hypothyroidism between the 2nd and the 4th weeks of life in preterm infants is recommended in order to avoid false negative on the first screening. The incidence of transient hypothyroidism in this population is high.

Objective and hypotheses: i) Analyse the utility of the second screening in our population of preterm infants. ii) Follow-up of those preterm infants with hypothyroidism.

Method: Prospective study of 434 premature infants with a gestational age <32 weeks and/or BW 1500 g (220 females) born between January 2003 and December 2013 with a negative first screening, were included. TSH and free T₄ by chemiluminescence assay (Siemmens) were determined between the 2nd and 4th postnatal weeks. SPSS14 were used for statistical analysis.

Results: 14 patients (3.2%) were diagnosed with hypothyroidism, 12 of them with a BW <1000 g. Gestational age (weeks) (S.D.): 27.4 (1.7); sex (F/M): 10/4; weight (g) 891 (215); multiple pregnancy: 5/14; SGA (one karyotype) two (47,XXY); and family history of hypothyroidism: 2; blood samples collection (days): 25 (15). Preterm infants with TSH 80.9 μU/ml (range: 12.9–312) and free T₄ 0.79 ng/dl (0.30) started treatment with L-T₄ at an age of 32.58 (13.9) days of life, at initial dose of 10.98 μg/kg per day (3.1) for 34.8 (5.9) months. All thyroid ultrasound demonstrated eutopic thyroid. At reevaluation ten of 14 patients (four continues treatment) showed: 20% permanent hypothyroidism (thyroid scintigraphy in a male demostrated hypocaptation on the left lobe); 20% hyperthyrotropinemia; and 60% TSH <5 μU/ml, suggesting transient hypothyroidism. However, follow-up of the patients with transient hyperthyroidism and two patients with normal function after discontinuation of treatment, develop permanent hypothyroidism. Studies on exon 10 of the TSH receptor gene performed in some patients were normal.

Conclusions: Our data emphasises the importance of follow-up thyroid function in preterm infants. Female and multiple pregnancy are factors associated with high risk of hypothyroidism. Long-term follow-up is indicated in these patients that require treatment in order to determine the definitive diagnosis.