The Journal of the Arkansas Medical Society Med Journal April 2019 Final 2 | Page 12

EDITORIAL PANEL: Chad T. Rodgers, MD, FAAP | Elena M. Davis, MD, MPH | William L. Mason, MD | Michael Moody, MD | J. Gary Wheeler, MD, MPS
Timely Congenital Hypothyroidism
Treatment Prevents Intellectual Disability
Y. ANNIE WANG, MD, and EMIR TAS, MD
C
ongenital hypothyroidism (CH)
causes inadequate thyroid
hormone production at birth.
It is one of the most common
preventable causes of intellectual
disability. Reported prevalence of CH
is 1:2000 to 1:4000. The prevalence
of primary CH in Arkansas in
2016 was approximately 1:1200.
Newborns with CH are frequently
asymptomatic with progressive
symptoms if they remain untreated.
Newborn screening is extremely
important for early diagnosis
and treatment before irreversible
neurologic damage occurs.
The American Academy of
Pediatrics and European Society
for Pediatric Endocrinology
guidelines are our references to help
practitioners diagnose and treat
CH in a timely manner to optimize
developmental outcomes and avoid
overtreatment. 1,2
The most common cause of CH
in the United States is secondary
to abnormal development of the
thyroid gland such as thyroid aplasia,
hypoplasia and ectopic thyroid. They
account for 75 percent of CH cases.
Thyroid dyshormogenesis accounts
for 10-15 percent of CH cases.
Primary CH can be permanent or
transient. These two forms of CH are
not clinically distinguishable.
Thyroid hormone is important
for energy metabolism, temperature
regulation, growth, central nervous
system maturation and bone
development. The fetal thyroid gland
starts producing thyroid hormone
by the 10th week of gestation. Prior
to this, maternal thyroid hormone is
critical for supporting the developing
fetus. Therefore, undiagnosed or
inadequately treated maternal
hypothyroidism may severely affect
fetal and neonatal development. At
delivery, there is a surge of thyroid-
stimulating hormone (TSH) due to
cold exposure. TSH elevation starts
30 minutes after birth, lasting 48
hours. During this surge, TSH levels
can reach 160 mIU/L.
Symptoms of CH are fairly silent
in newborns. Affected patients are
usually asymptomatic, rarely cry
and sleep most of the time. Physical
exam is usually unremarkable at
birth. If left untreated, classic signs
develop and include prolonged
jaundice, hypotonia with feeding
difficulty, umbilical hernia, soft
tissue myxedema, delayed skeletal
228 • THE JOURNAL OF THE ARKANSAS MEDICAL SOCIETY
development with decreased linear
growth and open fontanelles.
Further treatment delays lead
to developmental delay with
intellectual disability.
Newborn screening (NBS) for
CH occurs in all states but methods
vary. Whole blood is obtained by
heel stick onto filter paper after 24
hours of life. Collection before 24
hours may reflect the physiologic
surge in TSH (https://www.healthy.
arkansas.gov/images/uploads/
rules/NewbornScreening.pdf). In
Arkansas, primary TSH measurement
is done with back-up T4 measured if
TSH is above the cut-off threshold.
This method is highly sensitive for
primary hypothyroidism but may
miss central causes or delayed TSH
elevation due to prematurity. If the
CH screen is abnormal, confirmatory
screening with serum TSH and Free
T4 is recommended. Do not delay
treatment for patients with highly
elevated TSH pending confirmatory
test results.
Although imaging studies are
valuable in identifying the etiology
and permanence of CH, do not delay
initiation of treatment to perform
the study. Imaging is not required
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