Congenital Hypothyroidism in Babies
Content reviewed against published AAP, NIH guidelines
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If your baby has been diagnosed with or you suspect congenital hypothyroidism in babies, here is what the evidence says.
The short answer
Congenital hypothyroidism occurs when a baby is born with an underactive or absent thyroid gland, affecting about 1 in 2,000 to 4,000 newborns. Thanks to universal newborn screening, most cases are detected within days of birth before symptoms develop. When treated promptly with daily thyroid hormone medication, children develop normally with no intellectual impairment.
Key takeaways
- Congenital hypothyroidism occurs when a baby is born with an underactive or absent thyroid gland, affecting about 1 in 2,000 to 4,000 newborns. Thanks to universal newborn screening, most cases are detected within days of birth before symptoms develop. When treated promptly with daily thyroid hormone medication, children develop normally with no intellectual impairment.
- Usually normal when: Your baby's newborn screening came back normal for thyroid function
- Call your doctor if: You received a call that your baby's newborn screening showed an abnormal thyroid result — follow up immediately as directed
- Varies by age — see the age-by-age breakdown below
“Fever itself is not an illness — rather, it is a sign or symptom that the body is fighting an infection. Fever stimulates certain defenses, such as the white blood cells, which attack and destroy invading bacteria.”
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By Age
What to expect by age
0-3 months
Most babies with congenital hypothyroidism are detected through the newborn screening blood test (heel prick) done at 24-48 hours of life. Without screening, early signs can be subtle and include prolonged jaundice, excessive sleepiness, poor feeding, constipation, a hoarse cry, a large soft spot (fontanelle), and a puffy face. Treatment with levothyroxine should begin as soon as possible, ideally within the first 2 weeks of life.
3-6 months
If not detected and treated early, babies may show more obvious signs including poor growth, decreased activity, thick and dry skin, a large protruding tongue, and cool extremities. Untreated hypothyroidism at this stage can begin to affect brain development. Babies on treatment should be monitored with regular blood tests to ensure proper dosing.
6-12 months
Babies on appropriate thyroid replacement therapy should be growing and developing normally. Thyroid levels are typically checked every 1-3 months in the first year to adjust the dose as the baby grows. If your baby was diagnosed and treated early, developmental milestones should proceed on track.
12 months+
Children with congenital hypothyroidism need lifelong thyroid hormone replacement. With consistent treatment and monitoring, they are expected to have normal growth, intelligence, and development. Your pediatric endocrinologist will continue adjusting the medication dose as your child grows.
What Should You Do?
When to take action
- Your baby's newborn screening came back normal for thyroid function
- Your baby is alert, feeding well, and growing on their curve
- Mild jaundice resolved within the first 2 weeks
- Your baby has regular bowel movements and normal skin color
- Your baby seems unusually sleepy, difficult to rouse for feedings, or has a weak cry
- Your baby has prolonged jaundice lasting beyond 3 weeks combined with constipation
- Your baby has a noticeably large soft spot, puffy face, or thick tongue
- You received a call that your baby's newborn screening showed an abnormal thyroid result — follow up immediately as directed
- Your baby is increasingly lethargic, not feeding, and has cool mottled skin — this could indicate severe hypothyroidism or another serious condition
Doctor Visit Checklist
Bring this checklist to your next pediatrician visit to discuss Congenital Hypothyroidism in Babies.
Things to mention
- Your baby seems unusually sleepy, difficult to rouse for feedings, or has a weak cry
- Your baby has prolonged jaundice lasting beyond 3 weeks combined with constipation
- Your baby has a noticeably large soft spot, puffy face, or thick tongue
Observations to share
- Your baby seems unusually sleepy, difficult to rouse for feedings, or has a weak cry
- Your baby has prolonged jaundice lasting beyond 3 weeks combined with constipation
- Your baby has a noticeably large soft spot, puffy face, or thick tongue
Urgent signs to report immediately
- You received a call that your baby's newborn screening showed an abnormal thyroid result — follow up immediately as directed
- Your baby is increasingly lethargic, not feeding, and has cool mottled skin — this could indicate severe hypothyroidism or another serious condition
My notes
From ismybabyalright.com — free, evidence-based baby health guides
Related Resources
Jaundice Decision Tree
Assess jaundice severity in newborns and when to call the doctor.
Growth Percentile Calculator
Plot your baby's weight, length, and head circumference on WHO/CDC growth charts.
Month-by-Month Development
Detailed monthly development guides from birth through 24 months.
When to Call the Doctor
General guide on when to call the pediatrician, visit urgent care, or go to the ER.
Frequently asked questions
Is congenital hypothyroidism in babies normal?
When should I call the doctor about congenital hypothyroidism in babies?
When is congenital hypothyroidism in babies normal?
What causes congenital hypothyroidism in babies?
What should I mention to my pediatrician about congenital hypothyroidism in babies?
Is congenital hypothyroidism in babies normal at 0-3 months?
Is congenital hypothyroidism in babies normal at 3-6 months?
Should I go to the ER for congenital hypothyroidism in babies?
Does congenital hypothyroidism in babies go away on its own?
References
All content follows our editorial policy and is reviewed against published clinical guidelines.
2,705 evidence-based guides6 authoritative medical sources
Related Resources
Bottom line
Most cases of congenital hypothyroidism in babies are normal. Talk to your pediatrician if you received a call that your baby's newborn screening showed an abnormal thyroid result — follow up immediately as directed.
Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.
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