Risk factors associated with congenital hypothyroidism: a case-control study in southeast Iran.

Background and aim: Congenital hypothyroidism (CH) is known as one of the most common preventable cause of mental retardation. This study aimed to determine factors associated with CH in Iran.

Methods: This case-control study was conducted on 160 children under one year old in Zahedan in southeast Iran in 2016. The neonates who were born from March 1, 2015 to March 19, 2016 and had undergone a screening program for CH were the study population. The neonates with serum TSH > 10mIu/L and T4 < 6.5 or TSH > 30 mIu/L were considered as a case group. Each case was individually matched for sex, age at birth and place of residence with three neonates with normal TSH and T4 titers as a control group. Data was gathered using a standard checklist and analyzed using SPSS 20 and statistical tests, such as Chi-square and Fisher's exact tests. Multivariable logistic regression analysis was also used to identify independent predictors of CH.

Results: About 25 of the 40 patients with CH (62.5%) were male who, in the univariate analysis, the following explanatory factors had no significant association with CH: history of parental consanguinity, type of delivery, weight at birth, height at birth, age of mother, sampling time, nationality, and birth season (p>0.05). Although, multivariate analysis showed no significant association between the studied factors and risk of CH (p>0.05), the likelihood of CH was greater among neonates born to consanguineous parents (AOR: 1.78, 95% CI: 0.82-3.89), those who were born to lower height at birth (AOR: 1.82, 95% CI: 0.85-3.91), neonates born to mothers younger than 18 years (AOR: 2.43, 95% CI: 0.57-10.29) and those who were born in the summer (AOR: 1.76, 95% CI: 0.57-5.44).

Conclusion: None of the studied factors were predictors for CH. Since consanguineous marriages are frequent in the province, and it may be a major contributory factor, future studies should be conducted on the genetic causes.