Download congenital Hypothyroidism - Baylor College of Medicine

congenital Hypothyroidism
Baylor College of Medicine
Anoop Agrawal, M.D.
Case study- C.V.
C.V. is a FT, 4kg, 7 day old hispanic infant girl,
born to a 22 yo female, NSVD, GBS negative,
APGARS 9/9. You receive a call from the
Texas Department of Health stating C.V. has
an abnormal thyroid study on her newborn
screen.
What is your course of action?
Background
Thyroid development begins around 17th day
of gestation.
Hypothalamus releases TRH by 20th week of
gestation. T3 levels remain relatively low until
the 30th week.
Fetus is protected by increased activity of
deiodinase enzymes in the brain and maternal
thyroid hormone transfer across the placenta.
Placenta is impermeable to TSH.
incidence
In US - 1 : 3,500 live births
Females to Males - 2:1 ratio
Hispanic - 1:2000, White infants - 1:4000,
African American - 1:32,000
Children with Down syndrome have 35 fold
increase risk.
Congenital Hypothyroidism is the most
common treatable cause of mental retardation.
etiology of C.H.
What are the causes that result in lifelong
hypothyroidism?
Thyroid Dysplasia (agenesis, hypoplasia, or
ectopy) - incidence is sporadic in 85% of
cases
Dyshormonogenesis - inborn error of
thyroxine synthesis - 10% of cases
Secondary or Central Hypothyroidism
(1:25,000 - 100,000)
Etiology of C.H.
What are the causes of transient hypothyroidism?
Maternal or neonatal drug exposure
Iodine deficiency (in Europe 1:100 vs. in US
1:50,000 due iodized salt in foods)
Maternal antibodies - this form resolves in 1 to
3 months as antibodies are cleared
Gestational hyperthyroidism
Clinical manifestations
macroglossia
large fontanelles
hypotonia
umbilical hernia
prolonged unconjugated hyperbilirubinemia
hoarse cry
Clinical Findings
Finffmanifestations
95% of newborn will have no evidence of
disease
Can be associated with other congenital
malformations - mainly cardiac
renal and urologic deformities also seen
Newborn screening
All states screen for hypothyroidism - type of
testing is variable: T4 with TSH backup vs.
TSH alone
4 million infants are screened annually in US,
of which 1,600 will be diagnosed with
congenital hypothyroidism
Evaluation
case - c.v.
State TSH screen reported to be >400.
C.V. was called into the office the next day.
Thyroid function tests were performed via
venipuncture.
TSH > 54, free T4 - QNS, thyroglobulin <1
Started on thyroxine 10 mcg/kg/day - or 40
mcg per day. Referred to Endocrine Clinic.
Treatment
Start at 10-15 mcg/kg/day as single daily dose.
Initiation of hormone replacement with lthyroxine can wait until diagnostic labs
completed.
Certain milks and drugs can interfere with
thyroxine absorption: soy formulas, iron,
calcium, sucralfate, aluminum hydroxide, bile
acid sequestrants.
Treatment
How should thyroxine be administered to the
infant?
It is available only as a tablet
DO NOT HAVE THE PHARMACY
COMPOUND THE TABLET INTO A
SOLUTION.
Tablet should be crushed and given in a small
amount of milk or water.
Permanent vs. transient
How do you determine if child has permanent vs.
transient hypothyroidism?
After 3 years of age, discontinue therapy for 30
days. If low free T4 and high TSH are found,
then permanent is confirmed.
Thyroid scan or u/s - uncommonly performed.
If TSH rises above 20 mU/L after the first year of
life in setting of insufficient T4 therapy, then
likely to be permanent.
Follow-up care
AAP recommends the following schedule:
at 2 and 4 weeks after initiation of T4
treatment
every 1 to 2 months during first 6 mos.
every 3 to 4 months between 6 mos and 3yrs
every 6 to 12 months thereafter until growth
is complete
2 weeks after any change in dose
Follow up care
Serum T4 concentration should become
normal within 1-2 weeks of treatment.
Serum TSH should be normal within 1 month
of treatment.
Pedi endocrine
In HCHD, pediatric endocrinologist available at
Casa de Amigos
no outpatient pedi endo at BTGH
Depending on the type of Medicaid, a child
may be referred to either Casa de Amigos or
Texas Children’s.
conclusion
Congenital hypothyroidism is seen most
commonly in females, hispanics.
Thyroid dysgenesis is most common cause in
the US.
Iodine deficiency in the maternal diet is #1
cause worldwide.
Initiation with hormone replacement should not
be delayed.
Overall, long term outcomes are good.