Congenital Hypothyroidism Flashcards
The ___________ is the first endocrine gland to develop.
thyroid
What are the two embryonic origins of the thyroid?
Follicular cells: pharyngeal endoderm
Calcitonin-secreting cells: neural crest
The thyroid originates from endoderm between ____________.
the first and second pharyngeal arches
When does the thyroid complete its descent?
7th week
When do the follicular cells differentiate and begin to trap iodide?
Weeks 10-12
What are DIT and MIT?
Diiodotyrosine and monoiodotyrosine
TSH is detectable at _________ weeks gestation.
12
Although fetuses can make T4, maternal T4 can _______________.
pass through the placenta, thus limiting some of the fetal effects of congenital hypothyroidism
What is the incidence of congenital hypothyroidism?
1:2,000
Not having sufficient levels of T4 causes what in children?
Neurologic impairment and decreased linear growth
The most common cause of congenital hypothyroidism is _____________.
thyroid dysgenesis: caused by defective migration or differentiation of cells (this accounts for 85% of congenital hypothyroidism)
Less common causes of congenital hypothyroidism include _________________.
defects in thyroid hormone synthesis, TSH resistance, or central pituitary dysfunction
Dysgenesis of the thyroid can be ____________.
aplastic, hypoplastic, or ectopic
Some cases of thyroid dysgenesis (2%) are caused by ____________.
genetic defects (such as in PAX8)
What are signs and symptoms of congenital hypothyroidism?
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
When should newborn testing for congenital hypothyroidism occur?
At 2-3 days of age, after the TSH surge
There are two tests for congenital hypothyroidism: ________________.
T4: less than 10th percentile
TSH: greater than 20
The fetal HPA axis is functional at _____ weeks.
25
Thyroid dysgenesis is more common in ____________.
females
A baby with spiky hair, micrognathia, cleft palate, and hypertelorism might have a mutation in ________.
TITF-2
What is Pendred syndrome?
An autosomal recessive defect in pendrin – which pumps iodide into the colloid –that leads to hypothyroidism, goiter, and sensorineural deafness
Central hypothyroidism usually occurs with _____________.
other pituitary defects
