The Importance of Newborn Screening in the Detection of Congenital Hypothyroidism in Females

Abstract

Title: The importance of the newborn screen in detection of congenital hypothyroidism in females Authors: Mahera Husain, Rebecca Nunge, Maggie Rose, Julie Bittar. Michelle Zimmerman, MD Case: A nine-day-old female infant presented to the pediatric endocrinology clinic to establish care for congenital hypothyroidism. She was born vaginally at 36 weeks and 6 days, without complications to a 15-year-old mother with no past medical history or family history of chronic illnesses, including thyroid disease. At birth, she weighed 5 lb 10 oz, and was 19" long. Newborn screen showed TSH >1000 mcU/mL (reference 0.72-4.77) and free T4 of 0.3 ng/dL (reference 0.9-1.7). Exam revealed slightly indented anterior fontanelle, overriding sutures and a palpable posterior fontanelle. She had no palpable thyroid. Thyroid ultrasound showed no thyroid tissue in the neck. She was started on 37.5 mcg (16 mcg/kg) daily of levothyroxine. At two-month follow-up, TSH had decreased to 17 mcU/mL and free T4 1.1 ng/dL. Accordingly, her levothyroxine dose was increased. Two months later, her TSH was 25 mcU/mL and free T4 1.2 ng/dL. She will require lifelong thyroid supplementation and close follow-up. Conclusions: Newborn screening for thyroid defects is crucial to detect congenital hypothyroidism and prevent lifelong neurocognitive deficits and developmental delay. Clinical Significance: Congenital hypothyroidism has an incidence of 1:2000 in the United States. Females are twice as likely to be diagnosed with congenital hypothyroidism. Thyroid hormones are necessary for physical and neurological development, especially brain development. The prognosis for congenital hypothyroidism is excellent as long as medication is started early (as in this patient’s case). The severity of neurodevelopmental defects is related to the severity of the case, as well as how long the hypothyroidism is left untreated. The longer an infant goes without treatment, the more severe the deficit is, as demonstrated by lower IQ values. This case illustrates the need for comprehensive newborn screening for thyroid deficits. Newborn screening is a public health program whose recommendations vary by state, region, and country.