No type of human transformation is more distressing to look at than an aggravated case of cretinism. The stunted stature, the semi-bestial aspect, the blubber lips, retrousse nose sunken at the root, the wide open mouth, the lolling tongue, the small eyes half-closed with swollen lids, the stolid, expressionless face, the squat figure, the muddy dry skin, combine to make the picture of what has been termed the "pariah of nature." Not the magic wand of Prospero or the brave kiss of the daughter of Hippocrates ever effected such a change as that which we are now enabled to make in these unfortunate victims, doomed heretofore to live in hopeless imbecility, an unspeakable affliction to their parents and their relatives.
[Sir William Osler, 1897]
Remarkable progress in our therapy and knowledge of congenital hypothyroidism (CH) has been made since the demonstration by Murray in 1891 that thyroid extract could ameliorate many of the features of untreated cretinism, an advance described in dramatic detail in the above quotation from Sir William Osler. At this time, despite the striking improvement in the clinical features observed in affected patients, the associated developmental delay proved to be less amenable to therapy, and indeed some cognitive delay was thought to be inevitable. It was not until the 1970s that the importance of the timing of postnatal treatment in obviating the mental retardation was demonstrated convincingly. In a study by Klein et al. (1), 78% of infants with CH treated before 3 months of age but 0% treated after 6 months of age had an intelligence quotient (IQ) above 85, the mean IQ of the early treated group being 89, compared with an IQ of 54 in those treated late. Unfortunately, only one third of patients were recognized clinically within the first 3 months, and even fewer (10%) in the first month of life. The subsequent development by Dussault and Laberge (1A ) of a sensitive and specific RIA for the measurement of T4 in dried whole blood eluted from filter paper paved the way for the modern era of newborn screening for CH prior to the development of clinical manifestations.
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Embryology
Thyroid gland development and disease in children - PDF
Images of thyroid dysgenesis
