الفهرس 
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Abstract
Preterm delivery, as defined by the WHO 1999 is a delivery which occurs at less than 37 completed weeks of gestation(DeFranco et al, 2008). Worldwide 15 million babies are born preterm (<37 weeks’ gestation) every year (Chang H et al, 2013).
Spontaneous preterm labor accounts for 40% to 50% of all preterm deliveries (Nour 2012). Worldwide Preterm birth is one of the leading causes of neonatal morbidity and mortality (Oestergaard et al, 2011).
Respiratory distress syndrome (RDS) is a specific disorder that occurs almost exclusively in preterm infants and is due to deficiency, inactivation or dysfunction of pulmonary surfactant (Huiqing Sun et al 2013).
It occurs in 60-80% of infants less than 28 week of gestational age, in 15-30% of those between 32 and 36 weeks, in about 5% beyond 37 weeks, and rarely at term (Pradeep V Mally et al, 2013).
The diagnosis of RDS is based on a combination of the clinical features(tachypnea, subcostal, intercostal retractions, nasal flaring and cyanosis;on auscultation air movement is diminished despite vigorous respiratory effort), evidence of prematurity, exclusion of other causes of respiratory distress and characteristic radiographic appearance. The typical radiographic features consist of a diffuse reticulogranular pattern, giving the classic ground-glass appearance, in both lung fields with super-imposed air bronchograms (LIU Jing et al, 2010).
Variety of hormones affects surfactant synthesis and hence affects the occurrence and severity of RDS in neonate .Among these hormones are glucocorticoids and thyroid hormones (Angel P and Ana A 2013). The thyroid hormones are iodinated thyronines, primarily tetraiodothyronine (thyroxin or T4) and a lesser quantity of triiodothyronine(T3). Triiodothyronine(T3)isproduced by outer ring deiodination (ORD) of T4 in peripheral tissues. The majority of both thyroid hormones circulate in blood bound to plasma proteins (Liese and greet 2011).
This study explores the relationship between serum free T3, serum free T4, serum TSH levels and respiratory distress syndrome (RDS) in preterm infants. The study comprised 60 preterm infants with respiratory distress syndrome. They were selected from both Minia university hospital and Mallawy general hospital. They were compared to 30 preterm infants of the same gestational age not suffering from respiratory distress syndrome.