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MDCN 380: Course 4 > Abnormal TSH in Infancy > Flashcards

Abnormal TSH in Infancy Flashcards

1
Q

T/F: fetuses can make their own T4 after 6 weeks of development

A

false. Maternal T4 is the primary source of thyroid hormone
during the first 20 weeks fetal development

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2
Q

In utero, the TSH-FT4-FT3 feedback system is
immature, leading to relatively __) TSH ___ FT4

A

In utero, the TSH-FT4-FT3 feedback system is
immature, leading to relatively high TSH low FT4

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3
Q

T/F: you must alwasy treat transient confenital hypothyroidism in infancy to prevent brain damage

A

false. transient congenital hypothyroidism may not need
treatment – depend on expectation of natural history
and co-morbid conditions

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4
Q

__ __ is the most common
cause of preventable developmental delay

A

Congenital hypothyroidism is the most common
cause of preventable developmental delay

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5
Q

__ __ is the most common cause of
permanent congenital hypothyroidism

A

Thyroid dysgenesis is the most common cause of
permanent congenital hypothyroidism

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6
Q

not all instances of congential hypothyroidism may need treatmnet, but if it does need tx, you should start it within the ___ ___ of life. the treament should aim to normalize TSH in the infant by ___ month(s)

A

not all instances of congential hypothyroidism may need treatmnet, but if it does need tx, you should start it within the FIRST WEEK of life. the treament should aim to normalize TSH in the infant by 1 month(s)

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7
Q

note

A
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8
Q

Question
Most common cause of congenital hypothyroidism:

  • Iodine deficiency
  • Enzyme defect
  • Agenesis of thyroid gland
  • Lingual thyroid
  • Maternal exposure to anti-thyroid medication
A

AGENESIS OF THYROID GLAND; poor formation.

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9
Q

outline: thyroid function is negatively regulated by:

A

T3 levels. or t4 levels (since it cleaves into T3)

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10
Q

Embryology of thyroid gland
Day 16-17: Developing
from pharyngeal floor
and paired lateral
anlagen from the __
__ pouch
• Day 50: fusion of the
median and lateral
anlagen, thyroid gland
migrated to its definitive
location in the ___
neck

A

Day 16-17: Developing
from pharyngeal floor
and paired lateral
anlagen from the fourth
pharyngeal pouch
• Day 50: fusion of the
median and lateral
anlagen, thyroid gland
migrated to its definitive
location in the anterior
neck

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11
Q

READ:

Thyroid Ontogenesis
Embryogenesis – first 10-12 weeks of
development

• Hypothalamic maturation – weeks 4-5 through
week 30-35 of development

• Maturation of thyroid system function – weeks 20
through term

Maturation of fetal thyroid system
T4 (and T3)
•Week 10: capable of iodide concentration

  • Week 20: thyroid hormone production
  • Week 30: increase in T3

•At birth: T3 and T4 increased 2-6x, peaked at 24-36 hours

A
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12
Q

Truth or false:
FT4 can cross placenta

A

true. a bit.

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13
Q

Congenital Hypothyroidism
• Overall incidence ≈ 1:4000 live births
– 85% Sporadic
– 15% Hereditary

• Clinical assessment detects ≤ 5% of cases

• Common cause of preventable cognitive
impairment• ∴Neonatal thyroid screening performed
routinely in most developed countries
What is the etiology of transient congenital hypothyroidism?

A

Transient (10%)
– Prematurity
– Transient primary hypothyroidism
– Maternal anti- thyroid drugs and iodine
– Maternal TSH blocking antibody

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14
Q

What is the etiology of persistent congenital hypothyroidism?

A

Persistent (90%)
– Thyroid dysgenesis
– Dyshormonogenesis
– Iodide deficiency
– Maternal I131 ablation
during pregnancy – Thyroid hormone
resistance – TSH deficiency

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15
Q

Transient Congenital Hypothyroidism of prematurity:
premature babies born at around 20-26 weeks then there will be a __ free T4 and ___ TSH. Indication of hypothyroidism

A

premature babies born at around 20-26 weeks then there will be a LOW free T4 and HIGH TSH. Indication of hypothyroidism

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16
Q

Transient Congenital Hypothyroidism of prematurity
Treatment not
necessary unless:

A

unless
serum TSH elevated or
signs of central
hypothyroidism

17
Q

Transient Primary Hypothyroidism
• __ serum FT4 and __ TSH

• More common in Europe due to higher
prevalence of __ __ ?

  • Develop during first ___ weeks of life
  • Persists for 2-3 month
  • Treatment __
A

• Low serum FT4 and high TSH

• More common in Europe due to higher
prevalence of iodine deficiency ?

  • Develop during first 1-2 weeks of life
  • Persists for 2-3 month
  • Treatment recommended
18
Q

recall: Maternal Anti-Thyroid Drugs can cause hypothyroidism in baby

A
19
Q

Transplacental TSH Receptor Blocking Antibodies (TRB-Ab)
• 1-2 % of cases of congenital hypothyroidism
– (1:25,000-1:100,000)

• Associated with maternal __ __
disease

• Thyroid peroxidase antibodies not pathogenic
– TRB-Ab ’s linked to - __ hypothyroidism

– TSI linked to - __ hyperthyroidism

• Transient course resolving over 1-4 months in concert with declining passive maternal __ levels

A

Transplacental TSH Receptor Blocking Antibodies (TRB-Ab)
• 1-2 % of cases of congenital hypothyroidism
– (1:25,000-1:100,000)

• Associated with maternal autoimmune thyroid
disease

• Thyroid peroxidase antibodies not pathogenic
– TRB-Ab ’s - Congenital hypothyroidism –

TSIg’s - Neonatal hyperthyroidism

• Transient course resolving over 1-4 months in concert with declining passive maternal igG levels

20
Q

Common cause of primary (thyroid) persistnet congenital hypothyroidism in babies.

(note that central causes of persistant congenital hypothyroidism are issues of the hypothalamus and pituitary)

A

thyroid dysgenesis (75%) take up most cases

  • inborn error of thyroid metabolism (10%)
  • maternal I131 in pregnancy (it’s contraindicated)
  • thyroid hormone resistnace.
21
Q

Thyroid Dysgenesis involves an __, __, or __ Thyroid Gland

A

Thyroid Dysgenesis involves an Ectopic, Hypoplastic, or Athyrotic Thyroid Gland

  • most common cause of congenital hypothyroidism
  • usually sporadic
22
Q

which gender is more affected by thyroid dysgenesis

A

female/male ratio is 2:1 unexplained

23
Q

4 categories of Inborn Errors of Thyroid Hormone Metabolism (Dyshormonogenesis)

A
  1. iodide transport defects (+ neurosensory deafness pendred syndrome)
  2. organification defects
  3. thyroglobulin synthesis defect
  4. iodotyrosine deiodianse defecy
24
Q

Maternal I131 Ablation During Pregnancy

• I131 administration in pregnancy results in __
and usually severe __ __

• Maternal I131 crosses __ and trapped by fetal
thyroid

• I131 __ in pregnant females

A

Maternal I131 Ablation During Pregnancy

• I131 administration in pregnancy results in permanent
and usually severe congenital hypothyroidism

• Maternal I131 crosses placenta and trapped by fetal
thyroid

• I131 CONTRAINDICATED in pregnant females

25
Q

Hypothalamic/pituitary hypothyroidism is aka ____ hypothyroidism

A

central

26
Q

Hypothalamic / Pituitary Hypothyroidism

Associated clinical features? (6)

A
  1. persistent hypoglycemia
  2. micropenis/cryptorchidism
  3. prolonged neonatal jaundice
  4. other midline anomlaies like optic nerve hypoplasia
  5. persistently low serum T4 with low or normal TSH
  6. Isolated or multiple pituitary tropic hormone deficits.
27
Q

Symptoms of Congenital Hypothyroidism
gestation period? resp issues? tiredness? temperature? GI issues? liver?

A

• Prolonged gestation

• Respiratory distress
syndrome (in term infant)

  • Lethargy / Somnolence
  • Poor feeding
  • Hypothermia
  • Constipation
  • Prolonged jaundice
28
Q

Signs of Congenital Hypothyroidism
size? skull shape? tongue size? cry characteristic? Goiter presence? hernias? skin features?

A

Large for gestational age
infant

  • Enlarged posterior fontanel
  • Macroglossia
  • Hoarse cry
    • / - Goiter
  • Umbilical hernia
  • Cool, mottled, dry skin
  • Delayed relaxation of DTR ’s
29
Q

Question
• True or false
– Congenital hypothyroidism is the MOST
common preventable cause of developmental delay?

A

TRUE. Screening programs have lead to improved outcomes. most measure serum TSH

30
Q
A
31
Q

Compare post natal serum TSSH and T4 levels in term and premature babies

A

T4 lower in premature babies.

32
Q

Diagnosis of Congenital Hypothyroidism

A
33
Q

explain the bone age delay in congenital hypothyroidism

A

Distal femoral epiphysis
normally appears at ≈ 36
weeks gestational age

• Delay in ossification
suggestive of more severe
intrauterine
hypothyroxinemia

• Correlation with long-term
cognitive outcome

34
Q

principles of management of Congenital Hypothyroidism

A
  1. raise serum free T4 into normal range ASAP
  2. initial starting dose of thyroxin is 10-15 mcg/kg/day
  3. use thyroxin tablets only. liquid formulations unreliable
  4. prescribe consistent formulation. round to nearest 1/2 tablet
  5. keep serum TSH and free T4 in normal range
  6. adjust dosage in 12.5-25.0 mcg increments with serum TSH 4-5 weeks later.
35
Q

abnormal neuropsychologic outcomes in congenital hypothyroidism

A
  • Cognitive function
  • Gross motor development
  • Sensorineural hearing
  • Attentional measures
36
Q

Is My Child ’s Hypothyroidism Transient?

If permanence in question ≥ 2-3 yrs of age:
– __ thyroxin
– Repeat serum TSH, free T4 in 4-6 weeks
– Serum TSH and free T4 normal= __
– Serum TSH  ± free T4 decreses= __

If under 2-3 years of age, it’s permanent of thyroid scan reveals an ___ thyroid gland

  • is serum TSH >10-12 mU/L after 6-12 months of age while receiving ___ replacement.
A

If permanence in question ≥ 2-3 yrs of age:
– Discontinue thyroxin
– Repeat serum TSH, free T4 in 4-6 weeks
– Serum TSH and free T4 normal= TRANSIENT
– Serum TSH  ± free T4 decreses= NORMAL

If under 2-3 years of age, it’s permanent of thyroid scan reveals an ECTOPIC (EX/ LINGUAL) thyroid gland

  • is serum TSH >10-12 mU/L after 6-12 months of age while receiving thyroxin replacement.
37
Q

Neonatal Hyperthyroidism is rare. Symptoms, cause, resolution and treatment.

A

symptoms; irritability, flushing, tachycardia, hypertension, poor weight gain, thyroid enlargement

caused by transplacental passage of TSH receptor-stimulating antibody (TSA) from a mother with active or inactive GRAVES DISEASE.

  • resolves spontaneously in 3-12 weeks

TREATMENT: iodide or antithyroid drugs, steroids, propranolol.

38
Q
A

MDCN 380: Course 4 (83 decks)

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