Newborn suffers hypothermia in the extra-uterine environment, soon after birth, leading to a transient increase in TSH levels. Winters are the most stressful period in terms of cold stress.
Methods: In this observational study, data of cord blood TSH and time of birth 1500 neonates was taken from hospital records which were routinely screened for congenital hypothyroidism at a tertiary care hospital in northern India. Two groups of neonates were formed on the basis of their birth months. In the first group (i.e. winters), neonates born in December, January and February were taken while those born in April, May and June were included in the second group (i.e. summers).
Results: The cord blood TSH of neonates born in winters (median CBTSH=8.4 mIU/ml) was significantly higher (p=0.001) than that of neonates born in summers (median CBTSH=7.1 mIU/ml). The month wise distribution of CBTSH did also show the same pattern in winters and summers. The recall rate was also significantly higher (p=0.002) in winters (9.76%) than summers (4.84%).
Discussion: Thyroid hormones play essential role in successful transition to extra uterine life. There is sudden and transient increase in cord blood TSH especially in winters. It leads to increased recall rates (recall of neonates with cord blood TSH >20 mIU/ml for further assessment to rule out congenital hypothyroidism at 3rd postnatal day) for congenital hypothyroidism screening program. Thyroid hormones modulate the other hormones like thymulin in neonates, which are deserved to be studied to enhance immunity and decrease morbidities in them.