Faculty

Akanksha Parikh

Etiological Spectrum of Congenital Hypothyroidism - an Indian Perspective

In comparison to the West, a much higher incidence of congenital hypothyroidism (CH), as high as one in every 1130 live births being affected has been observed in India as per the national survey conducted by the Indian Council of Medical Research in 2018. In addition, dyshormonogenesis was reported as the most frequent etiology of primary CH. This high incidence has motivated some states of India to initiate universal newborn thyroid screening (NBTS), with more states to follow through soon. A large multicentred retrospective study in two southern states of India was undertaken to analyse 805 individuals who were attending the Paediatric Endocrinology clinics. The study also sought to analyse the real world use of NBTS as a tool for diagnosis. The median current age of the cohort was noted to be 10.3 years and 55.2% were females. A history of consanguinity was obtained in 18.5% of the patients. Although only 22% of the patients were diagnosed by a NBTS in this cohort, an improving trend of its use with time was evident. A majority of the NBTS was performed in babies born in private hospitals in tier 1 cities. Primary hypothyroidism accounted for 776 (96.3%), of whom 41.9% had thyroid dysgenesis, 26.5% had dyshormonogenesis and 28% remained unevaluated. Ectopic thyroid was the most common structural anomaly with suprahyoid being the most common location of the thyroid gland. The overall median age of diagnosis was 0.3 years and nearly one-third of children were diagnosed within the first month of life while the median age of diagnosis for children who had not undergone NBTS was 0.5 years. Neonatal jaundice (19%), developmental delay (27.7%) and short stature (26%) were the most common presenting symptoms which led to the diagnosis in this group. A thyroid nuclear scan was performed in 68% of the patients. In the dyshormonogenesis subgroup, the mean age of diagnosis was 3.3 years whereas in comparison, children with dysgenesis were diagnosed significantly earlier at 2.3 years (P = 0.006) and had a significantly more number of girls affected (P= 0.017). However, the two groups did not differ in prevalence of consanguinity, preterm birth, birth weight, as well as weight and height at presentation.

Traditionally, Western literature report structural anomalies of the thyroid gland to account for 80 – 85% of all cases of CH, particularly in the Caucasian population. Our study too revealed thyroid dysgenesis to be the most common etiology of primary hypothyroidism albeit to a much lesser extent. A higher degree of consanguinity may explain the relatively increased prevalence of dyshormonogenesis. The use of NBTS as a diagnostic tool is as yet suboptimal, particularly in the public setup and calls for a national policy for addressing the issue.

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