A 1-week-old boy is brought to the office by his parents to establish primary care. The infant was born at 38 weeks gestation to a 31-year-old woman, gravida 3 para 2, via scheduled repeat cesarean delivery. The infant weighed 3.2 kg (7 lb 1 oz, 50th percentile) at birth and had an unremarkable nursery course. The infant was discharged home at age 3 days and has been breastfeeding exclusively. He is voiding and stooling normally. Yesterday, the parents were notified of an abnormal result from newborn screening. Today, the infant weighs 3.21 kg (7 lb 1 oz). Physical examination is normal. Laboratory studies reveal a T4 level of 6 µg/dL (normal: 10-22 for the first week after birth) and a TSH level of 46 µU/mL. Which of the following is the most appropriate statement for this patient's parents?

Question

A 1-week-old boy is brought to the office by his parents to establish primary care.  The infant was born at 38 weeks gestation to a 31-year-old woman, gravida 3 para 2, via scheduled repeat cesarean delivery.  The infant weighed 3.2 kg (7 lb 1 oz, 50th percentile) at birth and had an unremarkable nursery course.  The infant was discharged home at age 3 days and has been breastfeeding exclusively.  He is voiding and stooling normally.  Yesterday, the parents were notified of an abnormal result from newborn screening.  Today, the infant weighs 3.21 kg (7 lb 1 oz).  Physical examination is normal.  Laboratory studies reveal a T4 level of 6 µg/dL (normal: 10-22 for the first week after birth) and a TSH level of 46 µU/mL.  Which of the following is the most appropriate statement for this patient's parents?

Quizplus · Accepted Answer

Explanation: 11ec2b69_becf_9c4a_8f63_ed71ea6b8b55_MD0005_00 11ec2b69_becf_9c4b_8f63_db406516e558_MD0005_00 Congenital hypothyroidism is a common and preventable cause of intellectual disability, affecting approximately 1 in 2,500 children in the United States. The majority of cases are due to thyroid dysgenesis (agenesis, hypoplasia, or ectopy). Most infants lack clinical signs of hypothyroidism at birth as maternal T4 crosses the placenta. However, as maternal T4 disappears, the infant may demonstrate decreased physical and mental activity (eg, lethargy, poor feeding, constipation, hypotonia). T4 is critically important for normal brain development and myelination. Infants with congenital hypothyroidism may experience permanent intellectual disability if hormone replacement is not initiated by age 2 weeks. Therefore, hypothyroidism is included in newborn screening programs throughout the United States. Newborn screening programs detect abnormal thyroid hormones (low T4, high TSH, or both) to identify infants with congenital hypothyroidism before clinical signs develop, which allows prompt treatment with levothyroxine and prevents intellectual disability. (Choice A) Iodine deficiency in the mother can cause decreased fetal and neonatal production of T4. Iodine deficiency is a relatively common cause of congenital hypothyroidism in the developing world but has virtually disappeared from the United States due to iodization of salt. (Choice C) Most infants with congenital hypothyroidism identified through newborn screening are asymptomatic due to the presence of residual transplacental maternal T4. The lack of clinical findings should not preclude further investigation and treatment. (Choice D) Waiting 2-4 weeks to treat congenital hypothyroidism places the infant at risk of intellectual disability as untreated patients may develop permanent neurological injury by age 2 weeks. (Choice E) Infants with congenital hypothyroidism have excellent outcomes if levothyroxine replacement therapy is started by age 2 weeks. Educational objective: Newborn screening can identify congenital hypothyroidism before symptoms develop. Low T4 and elevated TSH levels are confirmatory. Levothyroxine should be started as soon as possible to prevent permanent neurological injury. References: Pediatric hypothyroidism: diagnosis and treatment. (http://www.ncbi.nlm.nih.gov/pubmed/28534114) Hypothyroidism. (http://www.ncbi.nlm.nih.gov/pubmed/25086165)

A 1-Week-Old Boy Is Brought to the Office by His