May 152010
Congenital hypothyroidism-most are primary (i.e., from thyroid gland)- Sporadic or familial; with or without a goiter
Etiology:
o Most common is thyroid dysgenesis (hypoplasia, aplasia, ectopia); no goiter
o Defect in thyroid hormone synthesis–goitrous; autosomal recessive
o Transient neonatal hypothyroidism (resolves in 3 months)
o Transplacental passage of maternal thyrotropin
o Other:
~ Radioiodine exposure
~ Fetal exposure to excessive iodine (topical iodine antiseptics)
~ Fetal exposure to antithyroid drugs
~ Iodine deficiency or endemic goiter
o Central hypopituitarism
Clinical Manifestations:
- Clinical presentation is known as “cretinism’:
o Prolonged jaundice
o Large tongue
o Umbilical hernia
oEdema
o Mental retardation
o Developmental retardation
o Anterior and posterior fontanels wide
o Mouthopen
o Hypotonia
- Other findings-weight and length normal, feeding difficulties, apnea, sluggish,
decreased appetite, increased sleep, constipation, decreased temperature, skin cold
and mottled, peripheral anemia
- Laboratory evaluation:
o Low serum T 4 or free T 4; increased TSH
- Treatment-sodium thyroxine
Acquired hypothyroidism
- Hashimoto; thryroiditis is most common cause; may be part of autoimmune polyglandular
syndrome
- Also increased with Down, Turner, Klinefelter, and congenital rubella syndromes
- Typically presents in adolescence
Other causes-iatrogenic (medications, irradiation, surgery, radioiodine); systemic
disease (cystinosis, histiocytic infiltration)
Clinical presentation
- Many more girls than boys
- First sign usually deceleration of growth
- Then myxedema, constipation, cold intolerance, decreased energy, increased sleep,
delayed osseous maturation, delayed puberty, headache, visual problems
- Diffusely increased, firm, nontender thyroid; but may be atrophic so can be nongoitrous
- Laboratory and treatment-same as congenital
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