https://en.wikipedia.org/wiki/Congenital_iodine_deficiency_syndrome
| Congenital iodine deficiency syndrome | |
|---|---|
| Other names | Cretinism |
 | |
| Portrait by Eugène Trutat of a man with congenital iodine deficiency syndrome | |
| Specialty | Endocrinology |
Congenital iodine deficiency syndrome is a medical condition present at birth marked by impaired physical and mental development, due to insufficient thyroid hormone (hypothyroidism) caused by insufficient dietary iodine during pregnancy. It is one cause of underactive thyroid function at birth, called congenital hypothyroidism, and also referred to as cretinism.
If untreated, it results in impairment of both physical and mental development. Symptoms may include goiter, poor length growth in infants, reduced adult stature, thickened skin, hair loss, enlarged tongue, a protruding abdomen; delayed bone maturation and puberty in children; and mental deterioration, neurological impairment, impeded ovulation, and infertility in adults.
In developed countries, thyroid function testing of newborns has assured that in those affected, treatment with the thyroid hormone thyroxine is begun promptly. This screening and treatment has virtually eliminated the consequences of the disease.
Signs and symptoms
Iodine
deficiency causes gradual enlargement of the thyroid gland, referred to
as a goiter. 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. Other signs include thickened skin, hair loss, enlarged tongue,
and a protruding abdomen In children, bone maturation and puberty are severely delayed. In adults, ovulation is impeded and infertility is common.
Mental deterioration 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.
Cause
Disability-adjusted life years (DALY) lost from iodine deficiency in 2012 per million persons
52–163
181–217
221–221
222–310
320–505
512–610
626–626
653–976
984–1,242
1,251–3,159
Around the world, the most common cause of congenital hypothyroidism is dietary iodine deficiency. 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 for the synthesis of thyroid
hormones. Iodine deficiency is the most common preventable cause of
neonatal and childhood 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 in rain, introducing iodine to
soils. Soil deficient in iodine is most common inland, in mountainous
areas, and in areas of frequent flooding. It can also occur in coastal
regions, where iodine might have been removed from the soil by
glaciation, as well as leaching by snow, water and heavy rainfall.
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.
Differential diagnosis
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.
Prevention
There
are public health campaigns in many countries which involve iodine
administration. As of December 2019, 122 countries have mandatory iodine
food fortification programs.
Treatment
Congenital iodine deficiency has been almost completely eliminated in developed countries through early diagnosis by newborn screening utilizing a blood test for thyroid function.
Treatment consists of lifelong administration of 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. For 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.
Monitoring TSH blood levels every 2–3 weeks during the first months of
life is recommended to ensure that affected infants are at the high end
of normal range.
History
Cretinism (Styria), copper engraving, 1815
A 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,
King Carlo Alberto of Sardinia commissioned the first epidemiological study of congenital iodine deficiency syndrome, in northern Savoy
where it was frequent. 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 iodine deficiency. However, this disease was less mentioned
in medical books because it was erroneously considered to be an
aesthetic rather than a clinical disorder.
Congenital iodine deficiency syndrome was especially common in
areas of southern Europe around the Alps and was often described by
ancient Roman writers and depicted by artists. The earliest Alpine
mountain climbers sometimes came upon whole villages affected by it.
The prevalence of the condition 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
congenital iodine deficiency syndrome 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
neurological impairment with hypothyroidism due to iodine deficiency.
Both have been largely eliminated in the developed world.
Terminology
The term cretin was originally used to describe a person affected by this condition, but, as with words such as spastic and lunatic, it underwent pejoration and 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 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 the term "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:
