7. T3,T4,TSH do not cross placenta
in significant amount
7
8. Functions of thyroid hormones
Target tissue Mechanism
Nervous system Promote normal brain development
Heart • Increase number, affinity of beta adrenergic receptors
• Enhance responses to circulating catecholamine
Muscle Increase protein breakdown
Bone Promote normal growth and skeletal development
Gut Associated with carbohydrate absorption
Adipose tissue Stimulate lipolysis
Lipoprotein Stimulate formation of LDL receptors
Other • Stimulate oxygen consumption by metabolically active
tissues
• Increase metabolic rates
• Promote development of reproductive system
• Maturation of fetal lungs
8
9. Normal level of thyroid hormones
Age TSH (mIU/L) FreeT4 (pmol/L)
Birth-D3 OL <21 26-65
D4-D30 0.51-10.8 12-30
D31-1yr 0.39-7 9-16.1
≥ 1 yr 0.4-6 13.2-22.2
9
10. 2. Epidemiology
Hypothyroidism:
Incidence of congenital hypothyroidism
worldwide is 1:2500 - 4000 live births
In Malaysia, it is reported as 1:3666
It is the commonest preventable cause of
mental retardation in children
10
11. Hyperthyroidism:
Study in US (2008) concluded that the incidence
among individuals aged 0-11 years was 0.44 cases per
1000 population
The incidence among individuals aged 12-17 years
was 0.59 cases per 1000 population.
Thus, the incidence increases throughout childhood,
with a peak incidence in children aged 10-15 years
11
17. Treatment
Timing
Should begin immediately after diagnosis is
established
If features of hypothyroidism are present, treatment
is started urgently.
Duration
Treatment is life long
Except in children suspected of having transient
hypothyroidism where re-evaluation is done at 3
years of age.
17
18. Preparation
L-thyroxine tablets
The L-thyroxine tablet should be crushed,
mixed with breast milk, formula, or water and
fed to the infant.
Tablets should not be mixed with soy
formulas or any preparation containing iron
(formulas or vitamins), both of which reduce
the absorption ofT4.
18
20. Goal of therapy
To restore the euthyroid state
Serum FT4 level usually normalise within 1-2 weeks, and
thenTSH usually become normal after 1 month of
treatment.
Some infants continue to have high serumTSH
concentration (10 - 20 mU/L) despite normal serum FT4
values due to resetting of the pituitary-thyroid feedback
threshold.
Compliance to medication has to be reassessed and
emphasised.
20
22. Follow up
Monitor growth parameters and developmental
assessment.
Imaging studies
If the FT4 is low and theTSH value is elevated,
permanent hypothyroidism is confirmed and life-
long L-thyroxine therapy is needed.
22
23. Measurement schedule (FT4, TSH)
The recommended by American Academy of
Pediatrics
At 2 and 4 weeks after initiation ofT4 treatment.
Every 1 to 2 months during the first 6 months of life.
Every 3 to 4 months between 6 months and 3 years of
age.
Every 6 to 12 months thereafter until growth is
completed.
After 4 weeks if medication is adjusted.
At more frequent interval when compliance is
questioned or abnormal values are obtained.
23
24. Re-evaluation of patients likely
having transient hypothyroidism
Can be due to factors primarily affecting the
thyroid-like iodine deficiency or excess, maternal
TSHR antibodies, maternal use of anti thyroid
drugs
This is best done at age 3 years when thyroid
dependent brain growth is completed at this age.
Stop L-thyroxine for 4 weeks then repeat thyroid
function test: FT4,TSH.
24
28. Hashimoto thyroiditis
In older children, adolescence
+ve family h/o thyroid disease in 25-35% of
patient
Autoimmune process targeted the thyroid
gland thus resulting in fibrosis and atrophy of
thyroid glands
28
29. Firm, non tender, diffuse goiter
Onset after 6 years old
Associated with DM type 1, adrenal
insufficiency and hypoparathyroidism, down
syndrome, turner syndrome
29
38. A. Graves’ disease
Autonomous functioning of thyroid caused by
thyroid stimulating immunoglobulins (TSIs)
Increased thyroid hormones production and
peripheral conversion
Firm, diffuse goiter
Common in girls, in adolescence
38
42. B. Thyroid storm
Medical emergency.The mortality is 20 - 30 %.
Exacerbation of the hyperthyroid state with evidence
of decompensation in one or more organ systems
Precipitated by stress including concurrent infections,
surgery
Clinical diagnosis with features of severe
thyrotoxicosis, hyperpyrexia and neuro-psychiatric
manifestations such as delirium
42
48. Treatment
Minimally affected: observation
Severe:
Oral propranolol
PTU
Spontaneous resolution because ofTSIs
usually in 2-3 months of age
48
49. Take home message
Important to understood the physiology of
thyroid hormone
Congenital hypothyroidism – screening, treat
to prevent MR
Patient education and compliance to
treatment/follow up
49
51. References:
1. Nelson Essential of Pediatrics 6th ed
2. IllustratedTextbook of Pediatrics 3rd ed
3. Pediatric Protocol 3rd ed
4. Practice Guidelines forThyroid DisordersThe
Malaysian Consensus 2000
Thank You
51
Notas del editor
Overview thyroid hormones production n feedback regulation
T4T3 conversion mainly occurred in liver and kidneys
Maldescent thyroid-can function until early/mid childhood
Prolonged jaundice in hyperthyroidism-mechanism
Thyroid hormones need to relax the sphincter of oddi of biliary tract to secrete bile
Hypothyroidism associated with gall stone formation
Imaging study: us or radioisotope scan
When to do? Especially when solitary nodule
Normal eyes
McCune Albright syndrome is a genetic disorder of bones, skin pigmentation and hormonal problems along with premature puberty.