Pediatric Hypothyroidism

Question 1

Thyroid Hormone Synthesis Steps

Answer 1

Question 2

What kind of thyroid hormone determines the body’s feedback to it?

Answer 2

Free hormone

Question 3

Epidemiology of congenital hypothyroidism

Answer 3

1 in 2000-4000 babies
Hispanics/Asian/Native Americans > Whites > Blacks
F:M = 2:1

Question 4

Etiology of congenital hypothyroidism

Answer 4

• Absent thyroid or small ectopic thyroid
• Dyshormonogenesis (10%)
• Iodine deficiency (most common worldwide, rare here)
• Central hypothyroidism (5% or less, usually multiple pituitary hormone deficiency (MPHD))
• Transient (10%)
  Late maturation
  Antibodies from mother
  Goitrogens, Drugs

Question 5

Presentation of congenital hypothyroidism

Answer 5

Most infants are asymptomatic at birth
Need to screen
If untreated: lethargy, slow movement, hoarse cry, feeding problems, constipation, macroglossia, umbilical hernia, large fontanels, hypotonia, dry skin, hypothermia, prolonged jaundice

Question 6

Screening procedures
What problems can arise?

Answer 6

Measures T4 and/or TSH
Most states rely on TSH alone (high values) - Can miss central hypothyroidism or delayed TSH rise
False positives in early specimens

Question 7

How is it treated?
What are treatment goals?

Answer 7

Levothyroxine

Goals

• Serum free T4 or total T4 should be kept in the upper range
• Serum TSH under 5 mU/L (optimal 0.5-2)
• Growth and mental development that is as close to possible as their genetic potential

Question 8

How is mental retardation related to congenital hypothyroidism?

Answer 8

Inverse relationship between IQ and age at diagnosis of hypothyroidism
Compliance critical in first 3 years of life – Risk for irreversible damage
Hypothyroidism after age 3 does not affect brain development