Congenital hypothyroidism (CH) is among the most common conditions leading to intellectual disability, which can be prevented by early detection through newborn screening (NBS). In Mongolia, a regional screening program for CH was launched in 2000, which was supported by the International Atomic Energy Agency (IAEA) for the Asia Pacific Region. In our present study, a total of 23,002 newborns from nine districts in Ulaanbaatar were screened between 2012 and 2020, by the measurement of the thyroid-stimulating hormone (TSH) from dried blood spots, sampled 24 to 72 h after birth. The level of TSH was measured by the DELFIA assay. The overall CH prevalence confirmed at birth was 1/2091. The female-to-male ratio for CH cases was 1.8:1. The majority of patients were asymptomatic (72.7% of CH cases); umbilical hernia and cold or mottled skin were reported symptoms in patients with CH (27.3%). Thyroid dysgenesis (hypoplasia and agenesis) was the most common etiology, with a total of nine cases (81.8%) out of the eleven patients. The lapse between the birth date and the initiation of L-thyroxine treatment in CH-positive children was lower than 15 days in 63.64% of cases or 15 to 30 days in 36.36% of children. Further research is required to expand the screening coverage for CH in Mongolia.

Objective: The study aimed to identify the risk factors and clinical features of congenital primary hypothyroidism (CPH). Methods: A matched case-control study recruited all children diagnosed with congenital primary hypothyroidism and children without disease as a control between 2012 and 2020. Controls were matched on their gender and age. We collected information on demographic, clinical, and laboratory characteristics from patient’s medical records. Results: The birth weight (OR = 1.1; p = 0.001), gestational age (OR = 2.24; p < 0.001), maternal age (OR = 1.21; p < 0.001), additional congenital disabilities (OR = 1.1; p = 0.015) and maternal hyperthyroidism (OR = 1.21; p < 0.011) were significant factors for CPH. The baby’s height (OR = 0.2; p = 0.012), maternal gestational diabetes (OR = 0.2; p = 0.002) and being a twin (OR = 0.91; p = 0.010) were significant protective factors for CPH. In terms of clinical symptoms of CPH, 70.2% had shown no clinical signs at births in our study. The most commonly identified clinical signs were: umbilical hernia, open posterior fontanel, feeding difficulty, hypothermia, abdominal stiffness, cold or mottled skin, prolonged jaundice, and low muscle tone. Conclusion: Children with CPH are often symptom-free at birth, and several risk factors contribute to CPH.

Objectives: Our goal was to assess the outcomes of congenital primary hypothyroidism and evaluate forms of dysgenesis forms among children diagnosed with congenital primary hypothyroidism Methods: A cross-sectional study recruited all children diagnosed with congenital primary hypothyroidism between 2013 and 2020. All data, including demographic, clinical examination report, laboratory test results, and results of hand x-ray and ultrasound of thyroid glands, was collected from parents and medical records at hospitals. Results: Thyroid dysgenesis accounted for 76.3% of the causes of congenital primary hypothyroidism. Of all participants, 43% had an intellectual disability, and their average delayed bone age was 12.74 months. The most common abnormality of the thyroid gland was hypoplasia (76.3%). The age at diagnosis was the significant predictor for skeletal maturity delay (k = 0.25; 95% Cl = 0.17 -0.33; p < 0.001) and for intellectual disability (a OR = 1.04; p < 0.004). Conclusions: Dysgenesis of the thyroid gland was the main cause of congenital hypothyroidism. Age of diagnosis of congenital primary hypothyroidism was a significant determinant of irreversible adverse later outcomes among children in Mongolia.