Download hypothyroidism

HYPOTHYROIDISM
Importance of Thyroid in children
• Thyroid hormone is essential for the growth and maturation
of many target tissues, including the Brain, Skeleton &
Gonads in children.
• Abnormalities of thyroid gland function in children result not
only in the metabolic consequences of thyroid dysfunction
seen in adult patients,
but also unique effects on the growth and maturation
thyroid hormone-dependent tissues like brain, Skeleton &
Gonads.
Thyroid Gland
Hypothyroidism results from deficient
production of thyroid hormone
• Either from a defect in the gland itself (primary
hypothyroidism) or a
• Result of reduced thyroid-stimulating hormone (TSH)
stimulation (central or hypopituitary hypothyroidism).
2 types
Congenital
Acquired
• When symptoms appear after a period of apparently
normal thyroid function, the disorder may be truly
acquired or might only appear so as a result of one of a
variety of congenital defects in which the manifestation of
the deficiency is delayed.
• The term cretinism, although often used synonymously
with endemic iodine deficiency and congenital
hypothyroidism, is to be avoided.
Congenital Hypothyroidism
• Common disease - Commonest Endocrine
Disorder in infants
• Commonest cause of preventable mental
retardation
• Accurate diagnostic tests available
• Treatment is simple, Very cheap & effective
• If untreated, sequela are serious and
permanent
ETIOLOGIC CLASSIFICATION OF CONGENITAL
HYPOTHYROIDISM
PRIMARY HYPOTHYROIDISM
•
•
•
•
Defect of fetal thyroid development (dysgenesis)
Defect in thyroid hormone synthesis (dyshormonogenesis)
TSH unresponsiveness
Defect in thyroid hormone transport: mutation in
monocarboxylate transporter 8 (MCT8) gene
• Iodine deficiency (endemic goiter)
• Maternal antibodies: thyrotropin receptor–blocking antibody
(TRBAb, also termed thyrotropin-binding inhibitor
immunoglobulin)
• Maternal medications Iodides, amiodarone
Propylthiouracil, methimazole
Radioiodine
CENTRAL (HYPOPITUITARY) HYPOTHYROIDISM
• Mutations in genes
• TSH deficiency
• TRH deficiency
• TRH unresponsiveness
Clinical manifestations
• Most infants with congenital hypothyroidism are
asymptomatic at birth, even if there is complete agenesis
of the thyroid gland.
• This situation is attributed to the transplacental passage
of moderate amounts of maternal T4, which provides fetal
levels that are approximately 33% of normal at birth.
• Despite this maternal contribution of thyroxine,
hypothyroid infants still have a low serum T4 and elevated
TSH level and so will be identified by newborn screening
programs.
• Before neonatal screening programs, congenital
hypothyroidism was rarely recognized in the newborn
because the signs and symptoms are usually not
sufficiently developed.
• Birthweight and length are normal, but head size may be
slightly increased because of myxedema of the brain.
At birth
 Post maturity,large size
 Large posterior fontanelle
 Umbilical hernia
 Goitre
Early signs
 Flaccid,sleepy
 Poor feeding
 Constipation,abdominal distension
 Respiratory problems
 Peripheral cyanosis
Oedema

Prolonged jaundice

Cretinous appearance
Late signs

Large tongue

Hoarse cry

Dry skin,hair

Slow responses

Delayed development

Growth failure
Diagnosis
• Newborn screening-thyroid function tests
• In cord blood TSH- <<20 mIU/L
T4 - 6.6-22 mcg/dl
T3 - 0.3-0.7 ng/ml
• 3rd day TSH Preterm (28wk-36wk) -0.7-27mIU/L
Term
-1.0-38.9 mIU/L
T4
-8.2-19.9 mcg/dl
T3
- 0.75-2.6ng/ml
Types of screening.
•
•
•
•
Primary TSH test
Primary T4 test
Primary TSH with back up T4
Primary T4 with back up TSH
Primary TSH test
• Most common test
• This will miss secondary Hypothyroidism
• All newborns with TSH>20 should undergo repeat
testing from venous sample for TSH and T4
• Levels > 40 mu/ml with T4 < 6.5µgm/dl indicate
Hypothyroidism – Start treatment early
• If TSH 20-40; Repeat testing done at 2 weeks and
persistently elevated TSH or low T4 needs treatment
Isotope scanning

Should be done in all cases of CH if possible

Treatment should not be delayed if not available
 123I-sodium iodide is superior to 99mTc-sodium
pertechnetate for this purpose. But both are acceptable

Demonstration of ectopic thyroid tissue is diagnostic of
thyroid dysgenesis and establishes the need for lifelong
treatment

A normally situated thyroid gland with avid uptake of
radio isotope indicates a defect in thyroid hormone
biosynthesis
Treatment

Drug of choice is L-Thyroxine

Tablets of 12.5, 25, 50 & 100 µgm strength
available

Dose 10-15 µgm/Kg

Start with higher dose if TSH >100

Tablets can be crushed and given with
juce/milk
Monitoring




Monitor for TFTs 2 weeks after initiation of
Tt.
Then Monthly for 6m
Then 2-3monthlyfor 2 years
The dose of levothyroxine on a weight
basis gradually decreases with age to
4µgm/Kg in children & 2µgm/Kg in adult
Trial of stopping the Treatment
 If the permanent CH was not confirmed,
4
weeks trial by withholding the treatment
should be done at 3 years (After
completion of thyroid dependent brain
development)
 TFT s should be done after 4 weeks
 Marked increase of TSH indicates
permanent CH
 In some studies, upto 25% of CH were not
permanent
Prognosis
• Early diagnosis and adequate treatment
within the first 2 weeks of life result in
normal linear growth and intelligence
comparable with that of unaffected
siblings.
• Approximately 10-20% of children have
a neurosensory hearing deficit. All
children with CH should undergo
Hearing assessment
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