[36] Congenital Hypothyroidism Flashcards

1
Q

What is congenital hypothyroidism?

A

A condition of thyroid hormone deficiency present at birth

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2
Q

Why is congenital hypothyroidism important to detect in neonatal screening?

A
  • Relatively common

- Preventable cause of severe learning difficulties

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3
Q

What is the most common cause of sporadic congenital hypothyroidism?

A

Maldescent of the thyroid and athyrosis

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4
Q

What normally happens to the thyroid during early fetal life?

A

The thyroid migrates from a position at the base of the tongue to its normal site below the larynx

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5
Q

What happens to the thyroid in maldescent?

A

The thyroid remains as a lingual mass or a unilobular small gland

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6
Q

What is the reason for the failure of formation or migration of the thyroid?

A

Not well understood

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7
Q

Other than maldescent of the thyroid and athyrosis, what are the causes of congential hypothyroidism?

A
  • Dyshormonogenesis
  • Iodine deficiency
  • Hypothyroidism due to TSH deficiency
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8
Q

What is dyshormonogenesis?

A

An inborn error of thyroid hormone synthesis

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9
Q

What is hypothyroidism due to TSH deficiency usually associated with?

A

Pituitary dysfunction

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10
Q

What is the significance of hypothyroidism due to TSH deficiency being associated with pituitary dysfunction?

A

The pituitary dysfunction usually manifests in other ways before hypothyroidism is evident

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11
Q

What are the risk factors for dyshormonogenesis?

A

More common in ethnic groups with consanguineous marriage

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12
Q

What is the problem with the early diagnosis of congenital hypothyroidism?

A

They are difficult to differentiate from normal in the first month of life

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13
Q

What happens to the clinical features of congential hypothyroidism with age?

A

They become more prominent

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14
Q

What are the clinical features of congential hypothyroidism?

A
  • Feeding problems
  • Constipation
  • Faltering growth
  • Prolonged jaundice
  • Pale, cold, mottled dry skin
  • Coarse facies
  • Large tongue
  • Hoarse cry
  • Goitre
  • Umbilical hernia
  • Delayed development
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15
Q

How are most infants with congenital hypothyroidism picked up?

A

Routine neonatal biochemical screening

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16
Q

How does congential hypothyroidism present on routine neonatal biochemical screening?

A

Raised TSH in the blood, done by a blood spot on filter paper, called the ‘Guthrie card’

17
Q

What is recommended in infants who are identified to have congential hypothyroidism?

A

Thyroid imaging

18
Q

What is the purpose of thyroid imaging in congenital hypothyroidism?

A

Determine if the cause is due to thyroid dysgenesis, or due to hormone biosynthetic disorders

19
Q

What thyroid imaging may be used in congential hypothyroidism?

A
  • Ultrasound

- Radionucleotide scanning

20
Q

What is the treatment for congential hypothyroidism?

A

Thyroxine

21
Q

When should treatment with thyroxine be started in congenital hypothyroidism?

A

Before 2-3 weeks of age

22
Q

Why is it important that treatment with thyroxine is started before 2-3 weeks of age in congenital hypothyroidism?

A

To reduce the risk of impaired neurodevelopment

23
Q

How long is treatment required for in congenital hypothyroidism?

A

Life-long

24
Q

How is the dose of thyroxine determined in congenital hypothyroidism?

A

Titration of the dose to maintain normal growth, TSH, and T4 levels

25
Q

How is therapy monitored in congenital hypothyroidism?

A

Measuring serum TSH and T3 levels

26
Q

How often is therapy monitored in congenital hypothyroidism?

A
  • Every 1-3 months in 1st year
  • Every 2-3 months when 1-2 years of age
  • Every 4-6 months when >2 years of age
27
Q

What is the aim of treatment with thyroxine in congenital hypothyroidism?

A

To maintain T4 in upper 1/4 of normal range, and TSH in lower end of normal range.

28
Q

What are the complications of congenital hypothyroidism?

A

Without early hormone replacemenmt therapy, a number of adverse sequelae may occur, including;

  • Neurodevelopmental delay and mental retardation
  • Poor motor coordination
  • Hypotonia
  • Ataxia
  • Poor growth and short stature