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| Congenital iodine deficiency syndrome (Credit: wikipedia.org) |
Cretinism is
a condition of severely stunted physical and mental growth due to
untreated congenital deficiency of thyroid
hormone (congenital hypothyroidism) usually due to
maternal hypothyroidism.
Pathophysiology
Congenital hypothyroidism can be
endemic, genetic, or sporadic. If untreated, it results in mild to severe
impairment of both physical and mental growth and development.
Poor length
growth is apparent as early as the first year of life. Adult stature without
treatment ranges from 100 to 160 cm (3 ft 3 in to 5 ft
3 in), depending on severity, sex, and other genetic factors. In adults,
Cretinism results in mental deterioration, swelling of the skin, loss of water
and hair. Bone
maturation and puberty are severely delayed. Ovulation is
impeded, and infertility is common.
Neurological
impairment may be mild, with reduced muscle tone and coordination, or so severe
that the person cannot stand or walk. Cognitive impairment may also range from
mild to so severe that the person is nonverbal and dependent on others for
basic care. Thought and reflexes are slower.
Other signs
may include thickened skin, enlarged tongue, or a protruding abdomen.
Dwarfism may
also be caused by malnutrition or other hormonal deficiencies, such as
insufficient growth hormone secretion, hypopituitarism,
decreased secretion of growth hormone-releasing hormone,
deficient growth hormone receptor activity and
downstream causes, such as insulin-like growth factor 1 (IGF-1)
deficiency.
Treatment
Sporadic and
genetic cretinism results from abnormal development or function of the foetal
thyroid gland. This type of cretinism has been almost completely eliminated in
developed countries by early diagnosis by newborn
screening schemes followed by lifelong treatment with thyroxine (T4).
Thyroxine must
be dosed as tablets only, even to newborns, as the liquid oral suspensions and
compounded forms cannot be depended on for reliable dosing. In the case of
dosing infants, the T4 tablets are generally crushed and mixed with breast
milk, formula milk or water. If the medication is mixed with formulas
containing iron or soya products, larger doses may be required, as these
substances may alter the absorption of thyroid hormone from the gut. Frequent
monitoring (every 2–3 weeks during the first months of life) is recommended to
ensure that infants with congenital hypothyroidism remain within the high end
of normal range, or euthyroid.
Cause
Around the
world, the most common cause of congenital hypothyroidism is iodine deficiency.
Cretinism is therefore most probably due to a diet deficient in iodine. It has
affected many people worldwide and continues to be a major public
health problem in many countries. Iodine is an essential trace element,
necessary primarily for the synthesis of thyroid hormones. Iodine deficiency is
the most common preventable cause of brain damage worldwide. Although
iodine is found in many foods, it is not universally present in all soils in
adequate amounts. Most iodine, in iodide form, is in the oceans where the
iodide ions oxidize to elemental iodine, which then enters the atmosphere and
falls to earth as rain, introducing iodine to soils. Earth deficient in iodine
is most common inland and in mountainous areas and areas of frequent flooding,
but can also occur in coastal regions owing to past glaciation, and leaching by
snow, water and heavy rainfall, which removes iodine from the soil. Plants
and animals grown in iodine deficient soils are correspondingly deficient.
Populations living in those areas without outside food sources are most at risk
of iodine deficiency diseases.
Iodine
deficiency results in the impairments in varying degrees of physical and mental
development. It also causes gradual enlargement of the thyroid gland, referred
to as a goitre.
It is being combated in many countries by public health campaigns of iodine
administration.
History
Goiter is
the most specific clinical marker of either the direct or indirect insufficient
intake of iodine in the human body. There is evidence of goiter, and its
medical treatment with iodine-rich algae and burnt sponges, in Chinese,
Egyptian, and Roman ancient medical texts. In 1848, the Italian King Carlo
Alberto of Sardinia commissioned the first epidemiological study of goiter and
cretinism in his Haute-Savoy territories, where hideous cases of goiters and cretinism
frequently occurred in the population. In past centuries, the well reported
social diseases prevalent among the poorer social classes and farmers, caused
by dietary and agricultural monocultures, were: pellagra, rickets, beriberi,
scurvy in long-term sailors, and the endemic goiter caused by I-deficiency.
However, this disease was less mentioned in medical books because it was
erroneously considered to be an aesthetic rather than a clinical disorder. Endemic
cretinism was especially common in areas of southern Europe around the Alps and
was described by ancient Roman writers, and often depicted by medieval artists.
The earliest Alpine mountain climbers sometimes came upon whole villages of
cretins. Alpine
cretinism was described from a medical perspective by several travellers and
physicians in the late 18th and early 19th centuries. At that
time the cause was not known and it was often attributed to "stagnant
air" in mountain valleys or "bad water". The proportion of
people affected varied markedly throughout southern Europe and even within very
small areas it might be common in one valley and not another. The number of
severely affected persons was always a minority, and most persons were only
affected to the extent of having a goitre and
some degree of reduced cognition and growth. The majority of such cases were
still socially functional in their pastoral villages.
More mildly
affected areas of Europe and North America in the 19th century were referred to
as "goitre belts". The degree of iodine deficiency was milder and
manifested primarily as thyroid enlargement rather than severe mental and
physical impairment. In Switzerland, for example, where soil does not contain a
large amount of iodine, cases of cretinism were very abundant and even
considered genetically caused. As the variety of food sources dramatically
increased in Europe and North America and the populations became less
completely dependent on locally grown food, the prevalence of endemic goitre
diminished.
The early
20th century saw the discovery of the relationships of sporadic cretinism with
congenital hypothyroidism, and of endemic cretinism with hypothyroidism due to
iodine deficiency. Both have been largely eliminated in the developed world.
Etymology
The
term cretin was once used to describe a person affected by cretinism,
but, as with words such as spastic, and lunatic, it is
now considered derogatory and inappropriate. Cretin became
a medical term in the 18th century, from an Occitan and
an Alpine French expression,
prevalent in a region where persons with such a condition were especially
common (see below); it saw wide medical use in the 19th and early 20th
centuries, and was actually a "tick box" category on Victorian-era
census forms in the UK. The term spread more widely in popular English as a
markedly derogatory term for a person who behaves stupidly. Because of its
pejorative connotations in popular speech, health-care workers have mostly
abandoned cretin.
The
etymology of cretin is uncertain. Several hypotheses exist. The most
common derivation provided in English dictionaries is from the Alpine French
dialect pronunciation of the word Chrétien ("(a)Christian"),
which was a greeting there. According to the Oxford English Dictionary, the
translation of the French term into "human creature" implies that the
label "Christian" is a reminder of the humanity of the afflicted, in
contrast to brute beasts. Other
sources suggest that Christian describes the person's
"Christ-like" inability to sin, stemming, in such cases, from an
incapacity to distinguish right from wrong.
Other
speculative etymologies have been offered:
- From creta, Latin for chalk, because of the pallor of those affected.
- From cretira, Grison-Romanche creature, from Latin creatus.
- From cretine, French for alluvium (soil deposited by flowing water), an allusion to the affliction's suspected origin in inadequate soil.
