May 6, 2016 - Abnormal TSH in Infancy

Question 1

Embryogenesis of Thyroid Gland

Answer 1

Occurs in the first 10-12 weeks of life

Question 2

Maturation of Fetal Thyroid

Answer 2

Baby depends on the mom’s thyroid hormone level being normal so it can properly develop, particularly in the first half of pregnancy in utero. It’s not until week 30 that you have a lot of fetal T4.

Thyroid hormone can cross the placenta.

Question 3

Permeability of the Placenta

Answer 3

Iodine will cross no problem. The baby and the mother compete for the same shared pool of iodone.

TSH cannot cross as the placenta is impermeable.

T3 and T4 can cross the placenta in smaller amounts than iodine.

Question 4

Thyroid Dysgenesis

Answer 4

The most common cause (75%) of

Question 5

Symptoms of Congenital Hypothyroidism

Answer 5

1. Prolonged gestation
2. Respiratory distress syndrome (in term infant)
3. Lethargy
4. Poor feeding
5. Hypothermia
6. Constipation
7. Prolonged jaundice
8. Large for gestational age
9. Enlarged posterior fontanel

Question 6

Neonatal Thyroid Screening

Answer 6

Primary serum TSH (abnormal if >25)

Question 7

Managing Neonatal Hypothyroidism

Answer 7

Bring serum free T4 into the normal range ASAP by using thyroxin.

Keep serum TSH and free T4 in the normal range.