Supervisors info:
Τζέτη Μαρία, Αναπληρώτρια Καθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ, Επιβλέπουσα
Traeger – Συνοδινού Ιωάννα, Καθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Φρυσίρα Ελένη, Καθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Summary:
Background knowledge: Congenital hypothyroidism (CH) is the most frequently encountered Congenital Endocrinopathy, with prevalence 1:1500-3000 births, and may lead to intellectual disability if not diagnosed and treated promptly. The Hellenic Newborn Screening Program was initiated in 1980 and is carried out by Institute of Child Health (ICH) that receives and tests the Guthrie cards from all the maternity hospitals in Greece. More than 3,700,000 neonates have been screened over the last 35 years. ICH in collaboration with the Division of Endocrinology, Diabetes and Metabolism of the First Department of Pediatrics of the National and Kapodistrian University of Athens are responsible for the treatment initiation and the long-term clinical and hormonal follow-up of these patients.
Objective and hypothesis: To investigate if SNP’s found in genes associated with Thyroid hormones metabolic pathways can be correlated with some clinical features of CH such as L-T4 replacement therapy response.
Patients: Laboratory, clinical and ultrasonographic data were recorded from the medical records of children diagnosed with CH by the Greek neonatal CH screening program. Patients were selected according to the following criteria: age (>3 years old), natural conception, gestational age (>37 weeks), treatment initiation (<180 days from birth), monocytic pregnacy, non- syndromic, non- low birth-weight with a variety in LT-4 substitution therapy. 176 CH patients were divided to 4 subgroups according to their clinical features: Dysgenesis (Ν=54), Dyshormonogenesis (Ν=91). Sub-divided to Low dose (<3 μg/kg/d) (N=55) and High dose (>3 μg/kg/d) (N=36) groups and Transient (Ν=30).
Method: The method consists of: 1) DNA extraction from white blood cells 2) a PCR amplification (255 bp, 190 bp, 265 bp for rs225014, rs939348 and rs1991517) 3) restriction enzyme digestion (AfaI, RspRSII and BauI for rs225014, rs939348 and rs1991517 respectively) 4) gel electrophoresis.
Optimization studies were carried out in order to achieve the best discrimination between the three genotypes.
Results: No statistical significant difference found between subgroups for the three genotypes. Specifically THRa CC genotype proportion in Dysgenesis group (11,1%) was twice the Transient (6,60%) and four times more than Dyshormonogenesis group (3,20%). TSHR C/G allele genotype proportion in Dysgenesis group (14,80%) was twice the Transient (6,60%) and Dysormonogenesis (6,70%) group while in DIO2 smaller differences observed between groups. FT4 and dose was found to correlate to some genotypes but the affect was different between the groups. rs225014 (DIO2) appears to have an effect on the L-T4 dose and FT4 levels on Transient CH while rs939348 (THRa) appears to effect FT4 levels on CH patients with dyshormonogenesis. None of the examined SNPs correlated with any other clinical parameters.
Discussion: CH is a multifactorial and polygenetic disease with a variety of features and phenotypes making very difficult to find genetic biomarkers for decision-making and this is also evidenced by the contradictory consequences of the already published studies. The present study is the first attempt to correlate specific polymorphisms with the dose in children with CH with a known pathoetiology of the disease.
Keywords:
RFLPs, SNPs, Congenital Hypothyroidism, Correlation Study, L-T4 Substitution Dose
