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congenital Hypothyroidism

congenital Hypothyroidism. Baylor College of Medicine Anoop Agrawal, M.D. Case study- C.V.

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congenital Hypothyroidism

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  1. congenital Hypothyroidism • Baylor College of Medicine • Anoop Agrawal, M.D.

  2. 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?

  3. 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.

  4. 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.

  5. 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)

  6. 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

  7. Clinical manifestations • macroglossia • large fontanelles • hypotonia • umbilical hernia • prolonged unconjugated hyperbilirubinemia • hoarse cry

  8. 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

  9. 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

  10. Evaluation

  11. 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.

  12. Treatment • Start at 10-15 mcg/kg/day as single daily dose. • Initiation of hormone replacement with l-thyroxine 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

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