Valores de tsh neonatal en recién nacidos pretérmino de la provincia de alicante 2008-2012

Resum

Summary Background and objectives Neonatal TSH concentration of preterm infants (RNP) differs from TSH of term infant (RNT) due to the immaturity of the hypothalamic-pituitary-thyroid system. If we take the RNT decision limits for congenital hypothyroidism (CH) to RNP, we will obtain too many false negative. Because of that it¿s necessary establish specific TSH reference intervals (RI) for RNP. These will allow adjust decision limits for RNP, a better understanding and approach of screening of HC in this population group. Methods A cross-sectional study of all preterm infants (n = 6,526 RNP) in the province of Alicante is performed in a full five years (2008-2012) with dried blood samples obtained on paper of Generalitat Valenciana screening program of congenital metabolic disorders, analyzing the TSH of the double screening and collecting anonymously the followings variables: gestational age, birth weight, sex, twin, mother's age, days of life in cold extraction and birth month. As a control group we take all RNT of the same period (n = 79,019), excluding the HC. HC incidence in each group was analyzed, the differences between the TSH of RNT and RNP was also analyzed and the TSH distribution depending of days of life. To calculate the TSH IR of RNP we analyzed the influence of the collecting variables on the changes of TSH. IR performed according to the influential variables. Results A higher incidence of HC is observed in RNP (0.092 %) than in RNT (0.047 %), the difference of concentration of TSH is 0,22 mU/ml less in RNP and a similar distribution of TSH according days of life are observed in both groups. The highest prematurity degree have lower concentrations of TSH, increasing 0,06 mU/ml TSH for each gestational week. The RNP low birth weight (< 1500 g) have 0,28 mU/ml TSH lower than not low birth weight, born at coldest month have 0,10 mU/ml TSH increased than not born in the coldest month and sample early extracted (< 2 days) showed increasing 1,03 mU/ml TSH of not early. No significant differences in TSH were observed by sex, age of mother and being twin. IR were performed by groups of prematurity degree, subdividing into subgroups according to the influential variables: cold month and low birth weight (< 1500 g). Conclusions The TSH IR of RNP calculated, may be used in clinical practice, after adequate validation, allowing adjust specific TSH limits RNP decision after use and better interpretation of screening in RNP.