Hypothyroidism during Childhood = Cretinism  

Frequency: 1÷4,000 live births have congenital hypothyroidism

Cause: sporadic hypoplasia / ectopia of thyroid

• delayed skeletal maturation (= delayed appearance + growth of ossification centers, delayed epiphyseal closure)
• fragmented stippled epiphyses
• wide sutures / fontanels with delayed closure
• delayed dentition
• delayed / decreased pneumatization of sinuses + mastoids
• hypertelorism
• dense vertebral margins
• demineralization
• hypoplastic phalanges of 5^th finger

MR:

• reduced myelination of brain (usually beginning during midgestation)

OB-US:

• fetal goiter (especially in hyperthyroid mothers treated with methimazole / propylthiouracil / ¹³¹I)