Serum thyroid stimulating hormone, total and free T4 during the neonatal period: Establishing regional reference intervals.
BACKGROUND
Congenital hypothyroidism (CH), the most common etiology of preventable mental retardation in children, is estimated to be more prevalent among Asian population.


OBJECTIVE
Since thyroid function tests (TFTs) varied among different ages and geographical regions, in this study, the neonatal thyroid reference intervals in a healthy neonatal population is determined for the first time in Iran.


METHODS
A cross-sectional study performed on 246 healthy term newborns aged between 2 days and 1 month.


METHODS
Blood samples were obtained by venipuncture from all subjects. The median, 2.5(th), 5(th), 95(th), and 97.5(th) percentile of serum thyroid-stimulating hormone (TSH), as well as the total and free T4 were assessed among different age groups.


METHODS
Predictive Analytics Software (PASW Statistics 18) was used for the analysis.


RESULTS
Serum TSH, total and free T4 concentration peaked in 5(th) to 7(th) days of life, continued over 2 weeks, then decreased and started reaching to adult reference range. A significant negative correlation between age and serum concentration of TSH (P = 0.02), total T4 (P = 0.01) and free T4 (P = 0.01) was found.


CONCLUSIONS
This study yielded fairly different values for TFTs compared compared values found in other countries and also different from values reported for laboratory kits we used. These differences were assumed to be due to variations in ethnicity, age, and laboratory methods used. Due to the lack of international standardization, conducting multicenter studies helps in making a more precise evaluation of thyroid status in neonates.
Department of Pathology, Imam Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran ; Student's Scientific Research Center, Vali-e-Asr Hospital, Imam Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran.
Sara
S
Sheikhbahaei
Department of Pathology, Imam Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran ; Student's Scientific Research Center, Vali-e-Asr Hospital, Imam Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran.
Behnaz
B
Mahdaviani
Department of Pathology, Imam Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran.
Alireza
A
Abdollahi
Maternal, Fetal and Neonatal Research Center, Vali-e-Asr Hospital, Imam Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran.
Fatemeh
F
Nayeri
Congenital hypothyroidism; infant; newborn; reference values; thyroid hormones; thyrotropin