Acquired hypothyroidism due to autoimmune thyroiditis (Hashimoto's thyroiditis)

1. HYPOTHYROIDISM
DR.AMIT KUMAR
ASSISTANT PROFESSOR
PEDIATRICS

2. Probable questions
• Thyroid hormone synthesis
• Interpretations of thyroid function tests
• Congenital hypothyroidism
• Acquired hypothyroidism
• Endemic goiter
• cretinism
• symptoms
• Management of thyroid deficiency

3. Embryology of thyroid gland
Originates from an envagination of the floor of the pharynx.

4. The thyroid gland is one of the largest endocrine
glands.
Site : found in the neck, below the thyroid cartilage ,

5. 1.Loo
p
Thyroid Physiology

6. Physiology
2/2O

7. Transport & metabolism of thyroid hormones
T 4 and T3 are relatively lipophilic, their free forms in plasma are
in equilibrium with a much larger pool of protein-bound thyroid
hormones in plasma.
Protein binding:
 Maintains large pool of hormone that can readily be mobilized
as needed.
 Prevents excess uptake by the first cells encountered and
promotes uniform tissue distribution
The plasma proteins that bind thyroid hormones are Albumin,
Transthyretin (Thyroxine-binding Prealbumin) and Thyroxine-
Binding Globulin (TBG).

8. Transport & metabolism of thyroid hormones
.
Deiodination of T 4
to produce T3
Deiodinase activity varies among different tissues & at different
periods.
Thyroid hormones enter cells and act by binding to nuclear
receptors.T is 3-5 times more potent thanT . RT is inert.3 4 3
Hormone Total plasma level Free hormone level
T4 8 μg/dL 2 ng/dL (0.02%)
T3 0.15 μg/dL 0.3 ng/dL (0.2%)

9. Effects of thyroid hormones

10. Assessment of Thyroid function
• TSH
• Total T3 / T4
• Free T3/ T4
• USG of Thyroid gland
• Thyroid scan
• Anti TPO
• Anti TG
• TSH receptor blocking antibodies
• MRI Brain
• FNAC of thyroid gland

11. Age based reference values of thyroid hormones

12. 2.Relationship betweenT4and
TSH
T4
TSH

13. Case scenario 1
• T 4 - low
• T 3- Low
• TSH - markedly increased
• Interpretation ?
Primary
Hypothyroidism

14. Case scenario 2
• T 4- Low
• T 3- Low
• TSH- Low to Normal
• Interpretation ?
Central
Hypothyroidism

15. Case scenario 3
• T 4- normal
• T 3- normal
• TSH- Slightly High
• Interpretation ?
Subclinical
Hypothyroidism/
Obesity

16. Etiology
• Primary ( Thyroid >95%)
- Autoimmune Thyroiditis
- Enzyme defects : trapping, organification, thyroglobulin
synthesis, deiodination
- Iodine deficiency : endemic goiter
- Dysgenesis – Aplasia, dysplasia, ectopic
- Injury
- Goitrogens
- Transient Causes- Maternal TSH receptor blocking
antibody, Iodine excess, Maternal antithyroid drug

17. • Secondary or Tertiary ( Pituitary or
Hypothalamus)
- Malformations
- Genetic defects
- CNS insults
- CNS tumors
• Peripheral ( rare)
- resistance to thyroxine

18. CONGENITAL HYPOTHYROIDISM
most common
preventable
causes of mental
retardation.

19. Causes of permanent CH
Thyroid dysgenesis
Defects in thyroid hormone synthesis and
secretion (Thyroid dyshormonogenesis)
TSH resistance
Central (hypothalamic–pituitary)
hypothyroidism

20. Causes of transient CH
Antithyroid drugs
Iodine excess.
Worldwide, iodine deficiency
Transient hypothyroxinemia of prematurity
TSH receptor-blocking IgG antibodies
Large liver hemangiomas

21. Clinical features of Congenital Hypothyroidism
Most infants with congenital hypothyroidism are asymptomatic at
birth .
Birth weight and length are normal.
.
Wide posterior fontanelle/ constipation
Prolongation of physiologic jaundice. (Immaturity of hepatic
glucuronyl transferase).
Sluggishness, cry little
Poor appetite - feeding difficulties
Lack of interest, Somnolence
Protruberent abdomen, umbilical hernia
Macroglossia
Cold or mottled skin, hypotonia

22. Clinical features of Congenital Hypothyroidism
By 3-6 mo of age the clinical picture is fully developed, if
untreated.
The child’s growth will be stunted, the extremities are short,
and the head size is normal or even increased.
Coarse facial features: The eyes appear far apart, and the
bridge of the broad nose is depressed. The palpebral fissures
are narrow and the eyelids are swollen. The mouth is kept
open, and the thick, broad tongue protrudes.
Dentition will be delayed.

23. Clinical features of Congenital Hypothyroidism
Myxedema is manifested, particularly in the skin of the
eyelids, the back of the hands, and the external genitals.
Carotenemia can cause a yellow discoloration of the skin, but
the sclerae remain white.
Development is delayed.
Voice is hoarse.
Sexual maturation may be delayed.

24. Clinical features of Congenital Hypothyroidism

25. Approach to a newborn with positive
screening test for Congenital Hypothyroidism
Positive screening test on filter paper sample
Serum T / Free T , TSH4 4
Normal Abnormal
Thyroid Scan
Normal EctopicAbsent Uptake
Ectopic Thyroid Gland
START
TREATMENT -
DON’T WAIT
FOR SCAN

26. Approach to a newborn with positive
screening test for Congenital Hypothyroidism
Abnormal T , TSH & Normal Thyroid Scan4
Tg (Thyroglobulin) measurement
Normal Absent
Tg synthetic defect
Transient
congenital
hypothyroidism
Thyroid hormone
synthetic defect
or drug effect
TBII (Thyroid Binding Inhibitory
Immunoglobulin) measurement
Positive Negative

27. Approach to a newborn with positive
screening test for Congenital Hypothyroidism
Abnormal T , TSH & Absent uptake on Thyroid Scan4
Ultrasound
Normal gland No thyroid tissue
Thyroid agenesis
TSH receptor or
Thyroid hormone
biosynthetic defect
Transient
congenital
hypothyroidism
TBII (Thyroid Binding Inhibitory
Immunoglobulin) measurement
Positive Negative

28. Treatment of congenital hypothyroidism
Infants with low T4 and elevated TSH should be started on L-
Thyroxine as soon as the diagnosis is made.
Initial dose of L-Thyroxine is 10-15 μg/Kg/day.
Daily dose should be crushed and placed directly on the tongue
in the morning.
If a dose is missed, then double dose should be given on the
next day.

29. Treatment of congenital hypothyroidism
Goal of therapy: T4 should be kept in the upper half of normal range
with the TSH
suppressed in the normal range.
It takes less than a week for T
normalize.
4 to rise and 4-5 weeks for TSH to
Monitoring: T4 and TSH should be monitored according to following
schedule.
Growth and development of infant should be monitored.
:
0 to 6 months Every 6 weeks
6 months to 3 years Every 3 months
Beyond 3 years Every 6 months
6 to 8 weeks after any dose change.

30. Neonatal Screening Programme
• Dried blood sample after 72 hrs of life/ cord
blood
• T4/ TSH
• Appropriate cut offs of TSH should be used

31. Acquired Hypothyroidism
• Etiology
1. Autoimmune Thyroiditis- most common cause
2. Iodine Deficiency
3. Goitrogens
4. Secondary hypothyroidism
• F> M
• Goiter
• Association with other autoimmune condition

32. Evaluation
• Proper family history
• Examination : type of goiter
• Thyroid function tests
• Anti TPO( thyroid peroxidase)
• MRI brain
• Bone age

33. Clinical features
• Subtle
• Short stature
• Cold intolerance, lethargy, constipation
• Delay in dentition
• Poor school performance
• Delayed puberty
• Goiter
All children with unexplained
developmental delay, mental
sub normality and short
stature should be evaluated
for hypothyroidism

34. Management
• L- Thyroxine
• Dose is 100 ug/m2
• Gradual build of dose
• Empty stomach
• Follow up 3-6 monthly
• Maintain TSH in normal range
• Mostly life long therapy

35. Goiter
• Enlargement of Thyroid gland
• Thyromegaly- when lateral lobe of thyroid is
larger than the distal phalanx of child`s thumb
Estimation of thyroid size by palpation( WHO)
Stage 0 No goiter
1 A Goiter detectable only by palpation
1 B Palpable, visible when neck is fully extended
2 Goiter visible in normal neck position
3 Very large goiter, recognized from distance

36. Etiology( Goiter)
• May be associated with decreased, increased or
normal thyroid function
• Hypothyroidism- any cause except dysgenesis
• Iodine deficiency
• Infiltration( autoimmune,neoplasm,
hemochromatosis)
• Grave`s disease( TSH receptor stimulating
antibodies)
• Congenital

37. • Diffuse vs Nodular goiter
• Acute painful goiter
• Investigations-
thyroid function test
Anti TPO
USG
FNAC

38. Management of Goiter
• Directed towards the cause
• Thyroxin supplementation
• surgery

39. Iodine Deficiency Disorders( IDD)
• Endemic Goiter
- Iodine deficiency prevalent
- endemic goiter is present when the
prevalence of goiter in a defined population
exceeds 5 %
- TSH increased, Low T3, T4
- Iodine supplementation
- Epidemiological measures

40. • Endemic Cretinism
- endemic goiter, severe iodine def
- clinical features
deaf- mutism
squint
mental retardation
spastic/ rigid neuromotor disorder
short staure
coarse facial features
• Neurological cretinism
• Myxedematous cretinism

41. National Iodine Deficiency Disorder
control Programme(NIDDCP) 1992
• To reduce the burden of iodine deficiency to <10 %
among adults and < 5% among children
• Promotion of iodised salt
• Surviellance
• RDA of iodine – 40-120 ug for children upto 10 yrs
- 150 ug for older children and adults
- additional 25 ug during pregnancy
- additional 50 ug during lactation
• Iodination of salt- 1 part/ 25000 to 50000 parts of salt

43. • 1. a two year old child presented to the opd
with history of short stature, tiredness,
constipation. Examination revealed a palpable
goiter. Serum T4 decreased, TSH increased.
Most probable diagnosis
a) thyroid dysgenesis
b) thyroid dyshormonogenesis
c) TSH receptor blocking antibody
d) central hypothyroidism

44. • 2. A 14 year old female has thyroid enlargement,
firm, non tender, nodular. T 4= 5.2( normal), TSH
= 17.5 mIU/l . Most likely diagnosis
a) acute suppurative thyroiditis
b) Graves disease
c) Hashimoto thyroiditis
d) Simple colloid goiter
e) solitary thyroid nodule