Hypothyroidism

Hypothyroidism

Congenital hypothyroidism
1. detection is important
  1. CH relatively common
    1. incidence- 1 in 4000 births
  2. a preventable cause of severe learning difficulties
2. Causes
  1. maldescent of thyroid & athyrosis
    1. commonest cause of sporadic congenital hypothyroidsim
    2. thyroid migrates from sublingual position to normal site below larynx in early fetal life
      1. partial or complete failure of thyroid to develop may occur
        maldescent- thyroid remains as lingual mass or unilobular small gland
        reason for failure of formation or migration not understood
  2. dyshormonogenesis
    1. inborn error of thyroid hormone synthesis
    2. commoner in some ethnic groups w/ consanguineous marriage
    3. about 5-10% of congenital hypo cases
  3. iodine def
    1. commonest cause of congenital hypothyroidism worldwide
      1. but rare in UK
    2. preventable
      1. by iodination of salt in diet
  4. hypothyroidism due to TSH def
    1. isolated TSH def is rare
      1. about 1% of cases
      2. usually assoc w/ panhypopituitarism
        which manifests as
        growth hormone def, gonadotrophin def & ACTH def
        this -> hypoglycaemia & micropenis & undescended testes in affected boys
        the above appear before hypothyroidism becomes evident
3. clinical features
  1. hard to differentiate from normal in 1st month of life
    1. but become more prominent w/ age
  2. usually asymptomatic & picked up on Guthrie test (neonatal biochemical screening)
    1. otherwise
      1. failure to thrive
      2. feeding probs
      3. prolonged jaundice
      4. constipation
      5. pale, cold, mottled skin
      6. coarse facies
      7. large tongue
      8. hoarse cry
      9. goitre (sometimes)
      10. umbilical hernia
      11. delayed development
4. slight excess of other congenital abnormalities
  1. esp heart defects
5. Ix
  1. Guthrie test
    1. raised TSH in blood
    2. NB: thyroid dysfun secondary to pituitary abnormalities won't be detected on Guthrie as they'll have low TSH
  2. T4
    1. in some countries
6. Rx
  1. thyroxine
    1. start at 2-3 weeks old
      1. early Rx to prevent learning difficulties
      2. intelligence will be in normal range
    2. life-long oral replacement
      1. titrate to maintain normal growth, TSH & T4 levels
Juvenile hypothyroidism
1. usually caused by autoimmune thyroiditis
2. increased risk in children w/ Down or Turner syndrome
3. increased risk of developing other autoimmune disease
  1. vitiligo
  2. rheumatoid arthritis
  3. diabetes mellitus
  4. Addison's disease in some families
4. Rx
  1. thyroxine
5. clinical features
  1. goitre
    1. goitre can also be physiological in pubertal girls
  2. short stature/growth failure
  3. females> males
  4. cold intolerance
  5. cold peripheries
  6. bradycardia
  7. thin, dry hair
  8. pale, puffy eyes, w/ loss of eyebrows
  9. slow-relaxing reflexes
  10. constipation
  11. delayed puberty
  12. obesity
  13. slipped upper femoral epiphysis
  14. deterioration in school work
  15. learning difficulties

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	Created by v.djabatey over 10 years ago