Background: Preterm birth occurs once a baby is born prior to actually 37 weeks of pregnancy. Small to gestation is typically described as being lower than tenth percentile from the indexed population's allocation of birth weights by gestation or being in the bottom 10% of birth weights. Being short to gestational age (SGA) was connected with a number of negative consequences, including decreased cognitive and sensorimotor function. The goal of the investigation was to confirm the idea that preterm SGA babies have greater TSH amounts and a greater prevalence of thyroid disease. Methods: This prospective cohort research included 80 preterm neonates from El-Bagour General Hospital's neonatal critical care unit. Preterm infants were separated into two groups: The study group consisted of 40 SGA preterm neonates, whereas the control group consisted of 40 AGA preterm newborns. Results: In the current study, the findings shown a substantial difference in TSH between the AGA preterm neonates group and the SGA preterm newborns group. SGA preterm neonates had considerably lower mean FT4 and FT3 values than AGA preterm newborns. According to our findings, there was a significant reduction in thyroid dysfunction among AGA preterm neonates compared to SGA preterm newborns. Conclusion: Thyroid dysfunction was more common in preterm SGA babies.