Cretinism is caused by extreme hypothyroidism during fetal life, infancy, or childhood.
This condition is characterized by failure of body growth and mental retardation.
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What is the reason?
1. Congenital lack of a thyroid gland (congenital cretinism) OR
2. Failure of the thyroid gland to produce thyroid hormone
because of a genetic defect of the gland,
or iodine lack in the diet (endemic cretinism)
or fetal hypopituitary hypothyroidism
3. Maternal antithyroid antibodies that cross the placenta
How severe can endemic cretinism be?
The severity of endemic cretinism varies greatly, depending on the amount of iodine in the diet, and whole populaces of an endemic geographic iodine-deficient soil area have been known to have cretinoid tendencies.
Can a neonate with cretinism look normal?
- A neonate without a thyroid gland may have normal appearance and function because it was supplied with some (but usually not enough) thyroid hormone by the mother while in utero.
- T4 crosses the placenta, and unless the mother is hypothyroid, growth and development are normal until birth.
- A few weeks after birth, however, the neonate’s movements become sluggish and both physical and mental growth begin to be greatly retarded.
What if the mother is also hypothyroid?
When the mother is hypothyroid as well, as in the case of iodine deficiency, the child shows features of cretinism at birth. Also, the mental deficiency is more severe and less responsive to treatment after birth.
Can treatment reverse both the physical and mental effects of cretinism?
Treatment of the neonate with cretinism at any time with adequate iodine or thyroxine usually causes normal return of physical growth, but unless the cretinism is treated within a few weeks after birth, mental growth remains permanently retarded.
Why is early treatment of cretinism vital to the child's mental development?
- Unless the cretinism is treated within a few weeks after birth, mental growth remains permanently retarded.This results from retardation of the growth, branching, and myelination of the neuronal cells of the central nervous system at this critical time (mainly the first year of life) in the normal development of the mental powers.
- If treatment is started at birth, the prognosis for normal growth and development is good, and mental retardation can generally be avoided; for this reason, screening tests for congenital hypothyroidism are becoming routine.
What is the reason behind the potbelly appearance seen in cretinism?
- Skeletal growth in the child with cretinism is characteristically more inhibited than is soft tissue growth.This is because thyroid hormone is essential for skeletal growth whereas growth hormone is sufficient for soft tissue growth.
- As a result of this disproportionate rate of growth, the soft tissues are likely to enlarge excessively, giving the child with cretinism an obese, stocky, and short appearance.
The stunted skeleton combined with a normal soft tissue growth
in the abdomen gives it the appearance of a pot belly.
Cause and effect of a protruded large tongue
Occasionally the tongue becomes so large in relation to the skeletal growth that it obstructs swallowing and breathing, inducing a characteristic guttural breathing that sometimes
chokes the child.
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Ganong's review of Medical Physiology
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