Flashcards in Congenital Hypothyroidism Deck (22):
The ___________ is the first endocrine gland to develop.
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?
When do the follicular cells differentiate and begin to trap iodide?
What are DIT and MIT?
Diiodotyrosine and monoiodotyrosine
TSH is detectable at _________ weeks gestation.
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?
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:
- Large posterior fontanelle
- Prolonged jaundice
- Umbilical hernia
- Feeding difficulties
- Hoarse cry
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.
Thyroid dysgenesis is more common in ____________.
A baby with spiky hair, micrognathia, cleft palate, and hypertelorism might have a mutation in ________.
What is Pendred syndrome?
An autosomal recessive defect in pendrin – which pumps iodide into the colloid – that leads to hypothyroidism, goiter, and sensorineural deafness