Detailed presentation on congenital hypothyroidism including physiology, pathophysiology, newborn screening, management and follow up (including Sri Lankan practice).

1. CONGENITAL
HYPOTHYROIDISM
Dr. Sankha Jayasinghe
07/08/2018

2. Outline
Physiology of thyroid hormones
Pathophysiology of congenital hypothyroidism (CH)
Clinical manifestations of congenital hypothyroidism
Neonatal screening of CH
Management and follow up of CH

3. PHYSIOLOGY

6. T3 VS T4
T3
 3 – 4 times metabolically more
active than T4
 20% of T3 secreted into the
blood from gland
 80% of T3 by deiodination of
T4 in peripheral tissues
 Blood level of T3 : T4, 1 : 50

7. Normal thyroid physiology in the fetus
 The bilobed thyroid shape is evident by seven weeks of gestation
 Thyroid follicles containing colloid are seen histologically by 10 weeks
 Thyroglobulin synthesis can be detected at four weeks
 Iodine trapping at 8 to 10 weeks
 T4 and, to a lesser extent, T3 synthesis and secretion at 12 weeks
 Hypothalamic neurons contain TRH at six to eight weeks
 The pituitary-portal vascular system begins to develop at 8 to 10 weeks
 TSH secretion can be detected at 12 weeks

8.  Maturation of the hypothalamic-pituitary-thyroid axis occurs
during the second half of gestation, but completely normal
feedback relationships are not mature until one to two months
of postnatal life

9. The pattern of changes during gestation
In full-term babies, levels of TSH, T4,
and T3 rise sharply after birth, fall
rapidly during the first five days of
life, and then fall more gradually
between one and four weeks of life

10. The pattern of changes just after birth
 Serum TSH concentrations rise abruptly to 60 to 80 mU/L within 30 to 60
minutes after delivery in healthy term babies
 With exposure of the infant to a colder environment and clamping of the
umbilical cord.
 The serum TSH concentration then decreases rapidly to about 20 mU/L 24
hours after delivery and then more slowly to 6 to 10 mU/L at one week
 The initial surge in TSH stimulates thyroidal T4 secretion, so that serum
total and free T4 concentrations rise to a peak at 24 to 36 hours of life

11. Why are these thyroid hormones so important?

12. PATHOLOGY
Congenital hypothyroidism

13. Background
 Incidence is 1:2000 to 1:4000 newborns
 The incidence appears to be increased in twin births (1:900),
and even higher in multiple births (1:600)
 One of the most common preventable causes of intellectual
disability worldwide
 There is an inverse relationship between age at treatment
initiation and intelligence quotient (IQ) later in life
 The majority of cases are sporadic

14. PATHOPHYSIOLOGY

15. Congenital hypothyroidism- aetiology
 Primary hypothyroidism
 Central hypothyroidism
 Transient congenital hypothyroidism
 Defects in thyroid hormone transport
 Defects in thyroid hormone metabolism
 Defects in thyroid hormone action: Resistance to thyroid
hormone

16. Primary hypothyroidism
 Inadequate thyroid hormone production in the gland itself
 Thyroid dysgenesis
 80- 90 %
 agenesis, hypoplasia, or ectopy (2/3 of all dysgenesis)
 Dyshormonogenesis
 10-15%
 Autosomal recessesive
 Resistance to TSH

17. Central hypothyroidism
 Defects in the production of TSH, due to either hypothalamic or pituitary
dysfunction.
 May be associated with midline defects such as optic nerve hypoplasia
/septo-optic dysplasia or midline cleft lip and palate defects
 May follow birth trauma or asphyxia
 Can also be caused by insufficient treatment of maternal Graves'
hyperthyroidism during pregnancy, especially when maternal thyrotoxicosis
occurred before 32 weeks gestation ( possibly because insufficient TSH during
the period of maternal hyperthyroidism inhibit the normal growth and
development of the fetal thyroid)

18. Transient congenital hypothyroidism
 Iodine deficiency (Map)
 Iodine requirement/d ;
 Infants - 30μg/kg/d, Children – 90-120μg/kg/d, Adult - 150μg/kg/d
 Iodine exposure
 Exposure of the fetus or newborn to high doses of iodine
 Infants of mothers with cardiac arrhythmias treated with amiodarone
 When iodine-containing antiseptic compounds are used in mothers or
infants
 Maternal antithyroid drugs
 These drugs are cleared in days

19. Transient congenital hypothyroidism
 Maternal blocking antibodies
 Transplacental transfer of TSH-receptor blocking antibodies in mothers with
autoimmune thyroid disease
 Should also be considered if more than one infant born to the same mother (in
the same or multiple pregnancies) is identified as having primary hypothyroidism
by newborn screening
 Usually subsides in one to three months as the maternal antibodies are cleared
 Large hepatic hemangiomas
 May produce increased levels of type 3 deiodinase, resulting in "consumptive
hypothyroidism“
 Mutations in the dual oxidase (DUOX2) gene

21. Clinical manifestations
Congenital hypothyroidism

22. Asymptomatic newborns
 The vast majority (> 95%) have few, if any, clinical manifestations at
birth
 This is because some maternal T4 crosses the placenta, so that even in
infants who cannot make any thyroid hormone, umbilical cord serum
T4 concentrations are approximately 25 to 50 percent of those of
normal infants
 Birth length and weight typically are within the normal range
 Myxedema- increased OFC, birth weight often is at a relatively higher
percentile than birth length
 The knee epiphyses often lack calcification

23. Symptomatic infants
 Develop over the first few months of life
 Lethargy
 Hoarse cry
 Feeding problems, often needing to be awakened
to nurse
 Constipation
 Umbilical hernia
 Prolonged jaundice, primarily unconjugated
hyperbilirubinemia

24. Symptomatic infants
 Puffy (myxedematous) and/or coarse
facies
 Macroglossia
 Large fontanels
 Hypotonia
 Dry skin
 Hypothermia

25. In central hypothyroidism
 Hypoglycemia (growth hormone and adrenocorticotropic
hormone [ACTH])
 Micropenis (growth hormone and/or gonadotropins)
 Undescended testes (gonadotropins)
 Least commonly, features of diabetes insipidus (vasopressin)
 Hearing loss in an infant with central hypothyroidism may be a
tip-off to a TBL1X mutation

26. Associated congenital malformations
Following systems involve the most
 Heart
 Kidneys
 Urinary system
 Gastrointestinal tract
 Skeleton

27. NEWBORN SCREENING
Sri Lanka College of Paediatricians

28. Timing and technique
 Blood for screening is collected onto
filter paper cards after heel prick.
For full-term infants, the sample is
usually collected one to two days
after birth.
 Preterm neonates, low-birth weight
(LBW) and very low-birth weight
(VLBW) neonates and ill preterm
neonates admitted to neonatal
intensive care units should have
their screening either before
discharge or before 4 weeks of age,
whichever comes earlier.

29. Timing and technique
Neonates treated with dopamine or Dobutamine
should have their screening test two weeks after
stopping dopamine/ dobutamine.
If a heel prick screening test has not been done,
perform a venous blood TSH from day 3 to day 5 of life.
Cord blood is not recommended.

30. When to initiate treatment
 If capillary blood TSH concentration on neonatal screening is
≥40 mIU/L, perform TSH and fT4 (thyroid function tests) on
venous blood and start treatment. If results can be obtained on
the same day, treatment can be withheld till then.
 If capillary TSH concentration is 20-40 mIU/L, repeat venous
blood thyroid function tests (TFTs). Treatment can be withheld
until the venous blood TFT results are available, provided these
will be available on the following day.

31. Decision to start treatment based on the venous
blood TFTs
 If venous fT4 concentration is below the normal range for age, treatment
should be started immediately.
 If venous TSH concentration is >20 mIU/L, treatment should be started
even if the fT4 concentration is normal.
 If venous TSH concentration is between 6-20 mIU/L in a well-baby with a
fT4 concentration in the normal range for age,
 Repeat TFT in 2 weeks.
 Perform an ultrasound scan (USS) of the thyroid gland.
 If a small/ectopic thyroid gland is seen with TSH 6-20 mIU/L, then irrespective of
fT4value, thyroxine therapy should be started.
 If the thyroid gland is normal on USS with a TSH 6-20 mIU/L and a normal fT4, repeat
TFT every two weeks till TSH normalizes

32. IMAGING
Thyroid gland

33. Thyroid imaging
All children with CH should have an USS of the thyroid
gland.
If facilities are available, radioisotope scanning should
be done before starting treatment or within 3 days of
starting treatment.
Initiation of treatment should never be delayed
pending imaging.

34. Is it
effective?

35. Case scenario

36. Presentation
 10 day old baby girl, a product of non-consanguineous marriage was brought to
our attention due to high TSH levels detected at neonatal screening (90.5 mIU/l)
 Mother- 29y, B+, primi
 NVD, POA 39+1
 Bwt 2.355 kg (-2SD to -3SD), length 52 cm (+1SD to +2SD), OFC 30 cm (<-3SD)
 Uncomplicated antenatal Hx
 No thyroid diseases in the mother or in other family members
 Using iodinated salts
 Active, no feeding problems, BO normal, good cry

37. Examination
 No facial dysmorphism
 AF 3.5 cm, PF 1.5 cm
 Normal tone
 Normal skin texture
 Icteric +
 No neck lumps
 No umbilical hernia
 CVS, RS, abdominal findings are normal

38. Investigations
Venous 3rd G TSH > 100 mIU/l, fT4 4.58 micmol/l (D10)
SBR 285.28 micmol/l (D 8.4, ID 277.2)
Mother B+, Baby O -, DCT –
WBC 12,230, Hb 16.7g/dl, PLT 406,000
RET % 1.5%
Blood picture-reactive film

39. Management
Started on levothyroxine 15 micg/kg/d
Parent education
Inward monitoring for possible tachycardia for one day
USS of the neck planned
R/V in 2/52

40. At 2 weeks of treatments
3rd G TSH 9.78 (0.72- 13.1)
fT4 23.90 pmol/l (10.3- 25.8)

41. PHARMACOTHERAPY
Treatment and monitoring

42. Treatment and monitoring of CH
 Levothyroxine (L-T4) is the medication of choice.
 L-T4 should be initiated as soon as possible and during the first 2 weeks
after birth or immediately after confirmatory serum test results are
available.
 Initial dose of L-T4 is 10-15μg/kg per day.
 L-T4 tablet should be crushed and given dissolved in a few milliliters of
breast milk or water.
 Thyroxine should be given early morning on an empty stomach and breast
milk should be withheld for 30-45 minutes after the medication is
administered.

43. Monitoring of dose and follow-up
 Serum or plasma fT4 and TSH concentrations should be determined
between 8.00-9.00 a.m. before the morning dose of L-T4.
 At the first follow-up visit 2 weeks after starting L-T4, the fT4 level should
be checked and the dose adjusted accordingly.
 fT4 concentration should be maintained in the upper half of the age-
specific reference range.
 TSH should be maintained in the age-specific reference range.
 Any reduction of L-T4 should not be based on a single increase in fT4
concentration during treatment.

44. Suggested follow-up (once TSH/ fT4 levels
have normalized)
 During the first 6 months of life - fT4 and TSH should be checked every
6 weeks.
 6 months to 12 months of life - fT4 and TSH should be checked every 8
weeks.
 1 year to 3 years of life - fT4 and TSH should be checked every 3
months.
 After 3 years till growth is completed - fT4 and TSH should be checked
every 6-12 months.
 Additional evaluations should be carried out 4-6 weeks after any
change in L-T4 dose.
 Anthropometry, (OFC) measurements, and developmental assessments
should be monitored at each clinic visit.

45. RE-EVALUATION
Baby needs life long treatment?

46. Whom to consider?
 Those who had initial TSH >20 mIU/L with normal fT4 and
normal USS.
 All preterm and sick babies who required treatment.
 Those who had normal TSH levels immediately after
commencing treatment.
 In these patients treatment should be continued till 3 years of
age with regular clinical and biochemical monitoring.

47. Suggested procedure for re-evaluation
Reduce
dose of L-
T4 by
30%.
Check
TSH/ fT4
after 3
weeks.
Repeat an
USS of the
thyroid
gland
Decide

48.  If TSH >10mIU/L, CH is
confirmed and lifelong
treatment needs to be given
 If CH is not confirmed, reduce L-T4
dose gradually with repeat TFTs at 3
weekly intervals and stop treatment
thereafter.
 Repeat TFT after 3 months of
stopping treatment.

49. Prognosis
 For infants with congenital hypothyroidism who are treated
early (treatment begun between two and six weeks of life) and
appropriately treated through the first three years of life, the
prognosis for cognitive and physical development is good. The
prognosis worsens for infants who are detected later in life,
have more severe hypothyroidism, and/or who receive
inadequate doses of L-T4.

50. References
 Guidelines on management of congenital hypothyroidism in Sri Lanka. Sri Lanka J. Child Health
2015; 44(2):75-76
 Chapter 19. The Thyroid Gland. In:Ganong, W. F., Barman, S. M., Barrett, K. E., Brooks, H. L., &
Boitano, S. (2012). Ganong's review of medical physiology (24th ed.). New York, N.Y.: McGraw Hill
Medical.
 LaFranchi S.(2018). Clinical features and detection of congenital hypothyroidism. In Hoppin A,G.
(Ed).,UpToDate. Retrieved August,6, 2018 from https://www.uptodate.com/contents/clinical-
features-and-detection-of-congenital-hypothyroidism?topicRef=5840&source=see_link#H10
 LaFranchi S.(2018). Thyroid physiology and screening in preterm infants. In Hoppin A,G.
(Ed).,UpToDate. Retrieved August,6, 2018 from https://www.uptodate.com/contents/thyroid-
physiology-and-screening-in-preterm-
infants?sectionName=NEWBORN%20SCREENING&topicRef=5836&anchor=H7&source=see_link#H
12

51. References
 LaFranchi S.(2018). Treatment and prognosis of congenital hypothyroidism. In
Hoppin A,G. (Ed).,UpToDate. Retrieved August,6, 2018 from
https://www.uptodate.com/contents/treatment-and-prognosis-of-congenital-
hypothyroidism#H19859153
 Douglas S Ross D,S., (2018). Thyroid hormone synthesis and physiology. In Mulder
J,E,. UpToDate. Retrieved August,6, 2018 from
https://www.uptodate.com/contents/thyroid-hormone-synthesis-and-
physiology?topicRef=5840&source=see_link
 Thyroid Gland: Thyroid Hormone Synthesis. YouTube. Retrieved August,6, 2018
from https://www.youtube.com/watch?v=nnfpeTURSIU

52. THANK YOU!