Congenital hypothyroidism (CH) is defined as thyroid hormone deficiency present at birth. Thyroid hormone plays a vital role in the normal development of the central nervous system. Congenital Hypothyroidism is one of the most common causes of the preventable and treatable cause of mental retardation and intellectual disability. In various neonatal screening programs, it has an incidence of 1: 4000 live births [1]. It was first performed by Dassault in Quebec, Canada in1972 and they detected 7 cases of CH among 47000 newborns during 3 years [2]. The thyroid gland develops from a midline thickening of the pharyngeal floor and paired caudal extensions of the fourth pharyngobranchial pouches.

Thyroid hormone is very essential for brain development during 1-2 years of life. The need for neonatal screening for CH is essential as the majority of sign and symptoms does not exhibit until 3 month of age due to residual thyroid function or transplacental passage of maternal thyroid hormone [3]. If being delayed or neglected, it may cause mental retardation. The clinical manifestations are often subtle or not present at birth.

Common symptoms include decreased activity and increased sleep, feeding difficulty, constipation, and prolonged jaundice while myxedematous facies, large fontanels, macroglossia, a distended abdomen with umbilical hernia and hypotonia are common signs. To assess the various causes of congenital hypothyroidism one should ascertain the site of defect, whether it is in the thyroid gland, thyroid regulatory system, due to deficient thyroid hormone receptor activity or due to inborn errors of the thyroid hormone synthesis.

Most congenital hypothyroidism is caused by defects in the thyroid gland itself (primary hypothyroidism). Causes of primary congenital hypothyroidism can be broadly classified as the failure of the thyroid gland to develop normally (dysgenesis) or failure of a structurally normal thyroid gland to produce normal quantities of thyroid hormone (dyshormonogenesis). Thyroid dysgenesis which encompasses the spectrum of thyroid agenesis, hypoplasia, and ectopy—is the most common cause of congenital hypothyroidism, and its incidence (about 1:4000 infants) has not changed significantly over the last several decades.

The blood sample was taken in a sterile container under aseptic precautions, between 3-5 days of life to minimize the false positive high TSH values due to the physiological neonatal surge that elevates TSH level and causes T4, T3 changes in 1-2 days. In cases with a healthy newborn baby, sampling was done between 3-5 days.

Detailed antenatal history, parity, medical history, thyroid status, and community were recorded on a predesigned proforma. Details of the baby were recorded on a separate proforma. TSH was estimated within 24 h by chemiluminescence Immunoassay (kit supplied by Roche E411). Newborn with TSH value more than 20µ IU/L were labeled as a case of congenital Hypothyroidism and whose values were between 10-20 µIU/L were followed up with repeat TSH level after weeks.

Data analysis: All the data were analyzed by descriptive statistics and expressed in terms of percentage and tabulated form. The analysis was done on Microsoft Excel 2013.

Ethical permission: The study was approved by the institutional ethics committee. A well written informed consent was taken from all of the participants after explaining the details, benefits, and risks to them.

Interpretation of screening test: Venous TSH >20 mIU/L (serum units) is taken as the cut-off for postnatal screen samples after 48-72 hours of age is to be taken as positive newborn TSH between 10-20 mIU/L were taken for a second TSH sample at 7 to 10 days of age.

A total of 1363 babies were enrolled, but 1272 were an eligible candidate for the study period. Those, not eligible candidates received a blood transfusion, death within 3 days, left against medical advice (LAMA) or shifted to other hospitals and non-consenting of parents for the study. Out of the delivered babies, 820 were born by lower section caesarian section and 452 were vaginally delivered and there were 36 mothers who were hypothyroid and were on medication.

Numbers of term deliveries were 1109 and preterm deliveries were 163, with 665 (52.28%) males and 607 (47.72%) female babies. Of the total eligible neonates, 1109 were term babies and 163 were preterm babies with more than 34 weeks (Table 1).

for causing CH [6,7]. Deficiency of maternal iodine is another common contributing factor resulting in CH consequently leading to abnormal fetal depression. Transfer of excess of iodine to the fetus through placenta or secretion of iodine in breast milk may also result in CH among neonates [8,9].

As consanguinity is common in our country, CH although autosomal recessive in inheritance is expressed more commonly than in other developed countries.

Screening for CH by monitoring thyroid level at birth remains one of the most cost-effective tools in preventing mental retardation in these children. This neonatal screening is the norm in developed countries but unfortunately, such a nationwide program is non- existent in our country. There are two main screening ways for CH: primary T4 testing (with backup TSH) or primary thyroid-stimulating hormone (TSH) testing. In some states of USA, T4 estimation is done for screening while some US states screen T4 and TSH simultaneously [10], which may not be cost-effective for developing countries like India. The primary TSH screen is more sensitive and specific for the diagnosis of primary CH compared to the T4 screen [11].

In India, the first Newborn Screening program for CH was at BJ Wadia Hospital Mumbai in 1982 using cord blood TSH and subsequently in 1984 using postnatal dried blood spot [12,13]. A study conducted in 2001 reported that only 5%-10% of children have been diagnosed with CH under a screening program in India [14]. Therefore, India warrants an effective, robust, and cost-effective screening program. A study conducted by ICMR which screened for inborn metabolic disorders in neonates from the years 2007 to 2012 from Delhi, Mumbai, Chennai, Hyderabad, and Kolkata reported an incidence for CH of 1:1130 newborns. [15]

The most influential drawback of the present study is the small sample size. Large population-based studies are required to gauge and calculate the incidence of CH in our country. Therefore, India warrants a simple, effective, fast, and cost-effective screening program with adequate infrastructure, space, and resources as a part of Newborn screening.

In India, an attempt has been made to screen neonates for thyroid abnormalities at various centers, but a national program does not exist at present.

In the present study, the overall incidence is 1:636 while some studies showed 1in 248 and 1 in 1700 [25,26]. This may be due to less sample size and geographic variation. The prevalence of CH was 1.57 per thousand live birth. The male to female ratio in the present study was 1:1 while 1.2:1 was in Japan [27] in Bosnia [28] and 1.8:1 in Saudia Arabia [29]. However, some studies did not find any significant differences in mean TSH level according to sex [30,31] Out of the two babies who were diagnosed CH both were male. The first one had Down’s syndrome with cyanotic congenital heart disease (CHD) and second, it was of an elderly primi mother. At present both are under treatment with control.

Studies have reported that TSH levels increase with increasing gestational age however higher TSH levels in preterm than in terms have been reported. There is no statistical significance between low birth weight and normal weight babies with respect to theirs TSH values in the present study, but some studies have reported that low birth weight is related to high TSH [30].

Limitations: Geographic ethnic differences are responsible for this wide variation in incidence and a cohort size of 1272 samples is too less to access incidence. To have more conclusive evidence for the current findings, the studies to be conducted in the future should be designed in order to evaluate more babies/population as well as include other maternal and perinatal parameters in the analysis.

Timely diagnosis and treatment of CH are important in order to prevent psychomotor development disability &improve school progress. NBS is the need of the hour for early diagnosis of CH, which is simple, fast as well as cost-effective. Although universal newborn screening is implemented in developed countries; our country has still not implemented this universally. The policy should be formed so that this can be implemented at the grass-root level from ASHA workers to PHCs level to government/ private medical colleges.

New-born screening for CH if made compulsory in all centers has the potential to prevent intellectual impairment in India.