Congenital Hypothyroidism

Question 1

The ___________ is the first endocrine gland to develop.

Answer 1

thyroid

Question 2

What are the two embryonic origins of the thyroid?

Answer 2

Follicular cells: pharyngeal endoderm

Calcitonin-secreting cells: neural crest

Question 3

The thyroid originates from endoderm between ____________.

Answer 3

the first and second pharyngeal arches

Question 4

When does the thyroid complete its descent?

Answer 4

7th week

Question 5

When do the follicular cells differentiate and begin to trap iodide?

Answer 5

Weeks 10-12

Question 6

What are DIT and MIT?

Answer 6

Diiodotyrosine and monoiodotyrosine

Question 7

TSH is detectable at _________ weeks gestation.

Answer 7

12

Question 8

Although fetuses can make T4, maternal T4 can _______________.

Answer 8

pass through the placenta, thus limiting some of the fetal effects of congenital hypothyroidism

Question 9

What is the incidence of congenital hypothyroidism?

Answer 9

1:2,000

Question 10

Not having sufficient levels of T4 causes what in children?

Answer 10

Neurologic impairment and decreased linear growth

Question 11

The most common cause of congenital hypothyroidism is _____________.

Answer 11

thyroid dysgenesis: caused by defective migration or differentiation of cells (this accounts for 85% of congenital hypothyroidism)

Question 12

Less common causes of congenital hypothyroidism include _________________.

Answer 12

defects in thyroid hormone synthesis, TSH resistance, or central pituitary dysfunction

Question 13

Dysgenesis of the thyroid can be ____________.

Answer 13

aplastic, hypoplastic, or ectopic

Question 14

Some cases of thyroid dysgenesis (2%) are caused by ____________.

Answer 14

genetic defects (such as in PAX8)

Question 15

What are signs and symptoms of congenital hypothyroidism?

Answer 15

Generally, kids look well at birth but develop these symptoms later:

• Constipation
• Large posterior fontanelle
• Prolonged jaundice
• Macroglossia
• Umbilical hernia
• Feeding difficulties
• Hoarse cry
• Hypotonia

Question 16

When should newborn testing for congenital hypothyroidism occur?

Answer 16

At 2-3 days of age, after the TSH surge

Question 17

There are two tests for congenital hypothyroidism: ________________.

Answer 17

T4: less than 10th percentile
TSH: greater than 20

Question 18

The fetal HPA axis is functional at _____ weeks.

Answer 18

25

Question 19

Thyroid dysgenesis is more common in ____________.

Answer 19

females

Question 20

A baby with spiky hair, micrognathia, cleft palate, and hypertelorism might have a mutation in ________.

Answer 20

TITF-2

Question 21

What is Pendred syndrome?

Answer 21

An autosomal recessive defect in pendrin – which pumps iodide into the colloid –that leads to hypothyroidism, goiter, and sensorineural deafness

Question 22

Central hypothyroidism usually occurs with _____________.

Answer 22

other pituitary defects