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Zorluk: KolayPediatric Endocrine Disorders

A 4-week-old female infant is brought to the clinic by her parents due to increased sleepiness and poor feeding over the past week. The parents report that she has to be awakened for feeds and has had only one hard, pellet-like bowel movement in the last four days. She was delivered at home at 39 weeks gestation to a 28-year-old primigravid woman and did not undergo state-mandated newborn screening. Vital signs include a heart rate of 92/min and a temperature of 36.0°C (96.8°F). Physical examination reveals a lethargic infant with mild scleral icterus, a large anterior fontanelle, a protuberant abdomen with an umbilical hernia, and hypotonia. Which of the following serum laboratory patterns is most likely to be found in this patient?

  1. A
    Decreased thyroid-stimulating hormone (TSH) and decreased free thyroxine (T4)
  2. B
    Decreased thyroid-stimulating hormone (TSH) and elevated free thyroxine (T4)
  3. Elevated thyroid-stimulating hormone (TSH) and decreased free thyroxine (T4)Cevap
  4. D
    Elevated thyroid-stimulating hormone (TSH) and normal free thyroxine (T4)
  5. E
    Normal thyroid-stimulating hormone (TSH) and normal free thyroxine (T4)

Cevap

Elevated thyroid-stimulating hormone (TSH) and decreased free thyroxine (T4)
The infant's presentation is classic for congenital hypothyroidism. Because she was born at home, she missed the standard newborn screen that typically catches this condition before symptoms develop. The most common cause is thyroid dysgenesis (a primary thyroid gland defect). The failure of the thyroid gland to produce adequate thyroxine (T4) eliminates the normal negative feedback on the anterior pituitary gland, resulting in a compensatory elevation of thyroid-stimulating hormone (TSH).

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1
Analyze the clinical presentation and physical exam findings.
The infant shows lethargy, constipation, mild bradycardia, hypothermia, large anterior fontanelle, umbilical hernia, and hypotonia.
Identifying the classic constellation of symptoms is essential to recognizing the clinical syndrome of congenital hypothyroidism.
2
Identify the underlying etiology and location of the defect.
The most common cause of congenital hypothyroidism is thyroid dysgenesis (aplasia, hypoplasia, or ectopic gland), which is a primary defect of the thyroid gland.
Knowing the anatomical source of the disorder dictates the expected hormonal feedback loop alterations.
3
Deduce the expected laboratory findings based on the primary defect.
A primary thyroid defect leads to decreased free thyroxine (T4) production. The lack of negative feedback causes the pituitary gland to secrete high levels of thyroid-stimulating hormone (TSH).
This establishes the characteristic laboratory pattern needed to confirm the diagnosis of primary congenital hypothyroidism.

Anahtar Kavram

Clinical presentation and laboratory diagnosis of primary congenital hypothyroidism.
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Pediatric Endocrine Disorders

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