Congenital Hypothyroidism: Clinical Case and Viva Q&A
Clinical Case of Congenital Hypothyroidism
Clinical Case: Congenital Hypothyroidism
A 3-week-old female infant is brought to the pediatric clinic by her parents for a routine check-up. The parents report the following observations:
- Prolonged jaundice since birth
- Difficulty feeding and poor weight gain
- Excessive sleepiness and reduced activity
- Constipation
- Hoarse cry
On physical examination, the pediatrician notes:
- Weight: 3.1 kg (below 3rd percentile)
- Length: 49 cm (10th percentile)
- Head circumference: 35 cm (25th percentile)
- Pale, dry skin with mottling
- Large fontanelles
- Macroglossia
- Umbilical hernia
- Hypotonia
- Delayed relaxation of deep tendon reflexes
The pediatrician orders thyroid function tests, which reveal:
- TSH: 150 mIU/L (normal range: 0.5-5 mIU/L)
- Free T4: 5 pmol/L (normal range: 10-25 pmol/L)
Based on these findings, a diagnosis of congenital hypothyroidism is made. The infant is immediately started on levothyroxine replacement therapy, and follow-up appointments are scheduled to monitor growth, development, and thyroid function.
Clinical Presentations of Congenital Hypothyroidism
Clinical Presentations of Congenital Hypothyroidism
-
Classic Presentation
- Prolonged jaundice
- Feeding difficulties
- Constipation
- Lethargy and somnolence
- Large anterior and posterior fontanelles
- Macroglossia
- Umbilical hernia
- Hypotonia
- Cool, dry skin
- Delayed reflexes
-
Mild or Subclinical Presentation
- Subtle or absent clinical signs
- Normal growth and development initially
- Mild elevation of TSH with normal or slightly low T4
- May be detected only through newborn screening
-
Severe Presentation (Untreated)
- Profound intellectual disability
- Severe growth retardation
- Coarse facial features
- Myxedematous skin changes
- Persistent jaundice
- Severe constipation
- Hypothermia
- Bradycardia
-
Transient Congenital Hypothyroidism
- Temporary thyroid dysfunction
- May present with mild symptoms
- Often due to maternal factors (e.g., iodine deficiency or excess, anti-thyroid medications)
- Thyroid function normalizes within weeks to months
-
Syndromic Presentation
- Congenital hypothyroidism associated with other congenital anomalies
- Examples: Pendred syndrome (hearing impairment), Bamforth-Lazarus syndrome (cleft palate)
- May present with additional features specific to the syndrome
-
Late-Onset Presentation
- Subtle signs appearing in infancy or early childhood
- Mild developmental delay
- Growth deceleration
- Acquired goiter
-
Central Congenital Hypothyroidism
- Due to pituitary or hypothalamic dysfunction
- May present with additional pituitary hormone deficiencies
- Normal or low TSH with low free T4
- Often part of multiple pituitary hormone deficiency syndromes
Knowledge Check: Question and Answers for Medical Students & Professionals
This interactive quiz component covers essential viva questions and answers. It includes 30 high-yield viva questions with detailed answers.
What is the definition of Congenital Hypothyroidism (CH)?
Congenital Hypothyroidism is a condition of thyroid hormone deficiency present at birth, resulting from either a structural thyroid gland disorder or a defect in thyroid hormone biosynthesis.
What is the incidence of Congenital Hypothyroidism worldwide?
The worldwide incidence is approximately 1:3000-4000 live births, with higher rates in certain ethnic groups and geographical regions. The incidence is higher in iodine-deficient areas.
What are the main classifications of Congenital Hypothyroidism?
CH is classified into: 1) Primary (thyroid gland disorder), 2) Secondary (pituitary dysfunction), 3) Tertiary (hypothalamic dysfunction), and 4) Peripheral (thyroid hormone resistance). Primary CH accounts for 85% of cases.
What are the common causes of thyroid dysgenesis?
Thyroid dysgenesis includes: 1) Thyroid agenesis (complete absence), 2) Thyroid hypoplasia (small gland), 3) Thyroid ectopy (abnormal location), and 4) Thyroid hemiagenesis (partial absence). Ectopic thyroid is the most common form.
What genetic mutations are associated with thyroid dyshormonogenesis?
Key genetic mutations include: TPO (thyroid peroxidase), TG (thyroglobulin), NIS (sodium-iodide symporter), DUOX2, DUOXA2, IYD (dehalogenase), and SLC26A4/PDS (Pendred syndrome).
What are the clinical features of Congenital Hypothyroidism in neonates?
Key features include prolonged jaundice, feeding difficulties, constipation, lethargy, hypothermia, large anterior fontanelle, macroglossia, umbilical hernia, hypotonia, cold and mottled skin, and coarse facial features. However, many infants are asymptomatic at birth.
Why is early detection and treatment of CH crucial?
Early detection and treatment (within first 2 weeks) is crucial to prevent irreversible neurological damage and intellectual disability. Each month of delayed treatment can result in a loss of 5-10 IQ points.
What is the current recommended screening method for CH?
Primary TSH screening from dried blood spots (heel prick) at 48-72 hours of life is the most widely used method. Some programs use primary T4 with reflex TSH or combined T4 and TSH screening.
What are the TSH cutoff values used in newborn screening?
Most programs use a TSH cutoff of 20-25 mIU/L in the first 24-48 hours of life, lowering to 10-15 mIU/L after 72 hours. Values vary by program and screening methodology.
How should a positive newborn screen for CH be confirmed?
Confirmation requires serum thyroid function tests including TSH, free T4, and sometimes total T3. Thyroid imaging (ultrasound and/or scintigraphy) may be performed but should not delay treatment initiation.
What is the recommended initial treatment dose for CH?
Levothyroxine (L-T4) 10-15 μg/kg/day is recommended. Severe cases may require higher doses. Treatment should begin within first 2 weeks of life, earlier if possible.
How should L-T4 be administered to infants?
L-T4 should be crushed and mixed with small amount of breast milk or formula (not soy-based). It should be given at the same time each day, avoiding iron, calcium, and soy products within 4 hours of administration.
What is the monitoring schedule for CH in the first year of life?
Monitor TSH and FT4 at 2 and 4 weeks after treatment initiation, every 1-2 months during the first year, every 2-3 months during the second and third years, and every 3-12 months thereafter.
What are the target values for thyroid function tests during treatment?
Target FT4 in upper half of reference range (1.4-2.3 ng/dL) during first 3 years. TSH should be maintained between 0.5-5.0 mIU/L. Avoid overtreatment leading to TSH suppression.
What factors can affect L-T4 absorption?
Factors include: soy formula, iron supplements, calcium supplements, fiber, aluminum hydroxide, sucralfate, and certain medications. These should be separated from L-T4 administration by at least 4 hours.
What are the signs of overtreatment with L-T4?
Signs include irritability, sleep problems, diarrhea, frequent bowel movements, poor weight gain, accelerated bone age, craniosynostosis, and suppressed TSH levels (<0.05 mIU/L).
When should thyroid imaging be performed in CH?
Imaging can be performed after treatment initiation, typically at 3-5 days of age. Both ultrasound and scintigraphy (Tc-99m or I-123) provide complementary information about thyroid anatomy and function.
What is the role of genetic testing in CH?
Genetic testing is recommended in cases of dyshormonogenesis, family history, syndromic features, or permanent CH. It helps determine inheritance patterns and guides genetic counseling.
How can transient and permanent CH be distinguished?
Re-evaluation at age 3 years by gradually reducing or discontinuing L-T4 over 4-6 weeks. TSH elevation confirms permanent CH. Risk factors for permanent CH include severe initial hypothyroidism and thyroid imaging abnormalities.
What maternal conditions can cause transient CH?
Maternal conditions include: iodine deficiency or excess, anti-thyroid medications, TSH receptor blocking antibodies, and maternal thyroid disease. Most cases resolve within first few months of life.
What syndromes are associated with CH?
Associated syndromes include: Down syndrome, Turner syndrome, Williams syndrome, Pendred syndrome, Bamforth-Lazarus syndrome, and various genetic syndromes affecting thyroid hormone synthesis or action.
How does CH affect growth and development?
Untreated CH can cause severe growth retardation, delayed bone age, and permanent intellectual disability. Early treatment normalizes growth and development in most cases.
What is central hypothyroidism and how is it diagnosed?
Central hypothyroidism results from pituitary or hypothalamic dysfunction. It presents with low/normal TSH and low FT4. Additional pituitary hormone testing is required as multiple deficiencies often coexist.
What are the neurodevelopmental outcomes in treated CH?
With early treatment and good compliance, most children achieve normal intelligence. Subtle deficits in memory, attention, and visuospatial processing may persist. Severity at diagnosis and treatment timing influence outcomes.
How should CH be managed during illness or surgery?
L-T4 dose may need to be increased during severe illness or major surgery. Maintain regular monitoring of thyroid function. IV L-T4 may be required if oral administration is not possible.
What is the approach to CH in preterm infants?
Preterm infants have lower T4 and higher TSH values. Modified screening cutoffs and more frequent monitoring may be needed. Treatment thresholds may differ from term infants.
What are the long-term health implications of CH?
Patients require lifelong monitoring. They may have increased risk of obesity, metabolic syndrome, and cardiovascular disease. Regular health surveillance and lifestyle counseling are important.
How should adolescent transition of care be managed?
Transition planning should begin early. Focus on medication adherence, understanding of condition, and self-management skills. Adult endocrine care should be arranged with detailed transfer of medical information.
What are the effects of CH on fertility and pregnancy?
Treated CH does not typically affect fertility. Women need close monitoring during pregnancy with L-T4 dose adjustments. Preconception counseling is important.
What are the current challenges in CH management?
Challenges include optimal screening strategies, treatment individualization, adherence issues, identification of subtle cognitive deficits, and management of mild cases detected by lower TSH cutoffs.
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