| Thyroid
Disease in Childhood |
Index to this Health
Guide
General
Introduction
What Tests are Usually Done to Make a Diagnosis in
Your Child?
Congenital Hypothyroidism
Congenital Goitre
Hashimoto's Thyroiditis (Autoimmune Thyroiditis)
Graves' Disease (Hyperthyroidism)
Other Thyroid Disorders
Thyroid Disease and Growth
Treatment |
Health
Guides on Thyroid Disease
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General Introduction
Most thyroid disease
seen in adults also occur in children. Although there are some
differences in management, the principles remain the same. This
pamphlet is to be used together with the other Health Guides on
Thyroid Disease, which outline the causes and treatment of similar
conditions in adults.
It is very important
to explain to the child, according to their level of understanding,
where the thyroid is and what it does. A good way to describe
the shape of the thyroid is to compare it to a butterfly sitting
in the centre of the front of the neck over the windpipe and just
above the collar bone. The outline can be seen in a child by raising
the chin and tilting the head slightly back, especially if the
thyroid is larger than normal. Its function, or job, can be compared
to that of a furnace. If the thyroid is overactive (hyperthyroid),
it can be considered as turned up too high; if underactive (hypothyroid),
as turned down too low; or if the thyroid, no matter what its
size, is making the right amount of thyroid hormone, then the
thermostat is set just right.
The thyroid is a different
type of gland from the small round lymph glands which are easily
felt on the sides of every child's neck. The lymph glands are
there to protect against infection. The thyroid gland is there
to make thyroid hormone, a body chemical needed by all cells so
that they will work properly and at the right speed. The hypothalamus
and pituitary gland (see Health Guide 1),
are small downward extensions of the brain. They are about the
size of the end of a fingertip and are located just behind the
bridge of the nose and between the eyes. The hypothalamus produces
a hormone called TRH which travels down to command certain cells
in the pituitary to make another hormone called TSH (Thyroid Stimulating
Hormone). TSH in turn directs the thyroid to make thyroid hormone
(thyroxine) also called T4. If the thyroid makes too much T4,
then the hypothalamus and pituitary, in turn, cut down the production
of TRH and TSH. If the thyroid makes too little T4, then the level
of TSH rises to drive the thyroid to get bigger and to make more
thyroid hormone (T4).
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Graves'
Disease and Pregnancy
Treatment of Graves'
hyperthyroidism during pregnancy is different from that in non
pregnant women, since radioactive iodine cannot be given and surgery
should not be performed (particularly in the first and third trimesters
of the pregnancy for fear of inducing a miscarriage). Because
of the immunosuppressive effect of pregnancy, antithyroid drugs
can be given in doses lower than with non pregnant patients. Overtreatment
of the hyperthyroidism with antithyroid drugs can affect the baby's
thyroid since the drugs cross the placenta into the baby's bloodstream.
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What
Tests are Usually Done to Make a Diagnosis in Your Child?
A blood sample for
TSH and T4 measurement, taken from a vein in the hand or arm,
tests to see if the thyroid function is normal. For children on
medication, it checks that the dose of medicine is right.
In children with hypothyroidism
an x-ray of the hand and wrist (knee in infants) may be taken
to estimate the degree to which there has been a delay in bone
growth.
It is usually unnecessary
to take x-rays of the thyroid unless the enlargement is uneven
and a lump or nodule is suspected. If there is a nodule an ultrasound
will help to tell if it is fluid-filled or solid. A thyroid x-ray,
called a scan, uses a very safe weak radioactive material to see
if the thyroid behaves in a normal way by taking up the radioactivity
evenly. A spot with no uptake of radioactivity may be described
as "cold" and could be a tumour. In this case a thyroid biopsy,
using a small needle may be done. The needle is placed in the
thyroid to remove some cells for examination under a microscope.
Older children tolerate this procedure well without sedation.
If they are scared, a hand held by a parent and some anaesthetic
cream helps.
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Congenital
Hypothyroidism
Congenital hypothyroidism,
affecting one in 4000 newborn babies, used to be a major cause of
mental retardation. Development of the brain, as well as normal
growth of the child, is dependent upon normal levels of thyroid
hormone.
A thyroid blood test
(TSH or T4) is routinely done on a small heel-prick blood sample
obtained between day 2 and day 5 after birth. If the TSH is high
(or the T4 is low) the findings are confirmed by repeating the test
on a venous blood sample.
The thyroid gland begins
as a few cells at the back of the tongue in early fetal life. These
cells increase in number and travel down to the normal position
in the front of the neck during the first weeks after conception.
The developing fetus depends mainly upon its own thyroid gland to
make thyroid hormone. In infants with congenital hypothyroidism,
the thyroid gland, for reasons that are unknown, may either fail
to develop or be much smaller than normal. The position of this
poorly developed thyroid gland may be anywhere from the back of
the tongue to its normal place in the front of the neck. About 10%
of infants with congenital hypothyroidism will have an inherited
inability to make thyroid hormone although the thyroid gland is
present (congenital goitre). Rarely the thyroid may be temporarily
unable to make thyroid hormone. Antibodies, present in the blood
of a mother with thyroid disease, may cross the placenta and temporarily
block the baby's own thyroid from working. Except for these few
babies, the hypothyroidism is permanent.
Now that a screening
test is universally available, this condition can be recognized
and treated rapidly. Life-time treatment with a daily thyroid tablet
will prevent mental retardation, and will result in normal growth.
The dose is monitored and adjusted throughout infancy and childhood
by measurement of the levels of TSH and T4 in the blood.
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Congenital
Goitre
There are several uncommon
inherited causes of goitre (thyroid enlargement) in children. Although
these children may be hypothyroid, thyroid function is usually normal
and the only abnormality is a thyroid enlargement. The treatment
is to give thyroid hormone which causes the thyroid to shrink somewhat
by "shutting off" TSH production by the pituitary gland. One of
these conditions is associated with hearing loss, which may also
be present in the other family members.
Hashimoto's
Thyroiditis (Autoimmune Thyroiditis)
The most frequent cause
of thyroid enlargement in children and adolescents is Hashimoto's
thyroiditis. This is more common in girls and in those with a family
history of Hashimoto's or other thyroid disorders. Apart from the
enlarged thyroid, there may be no other changes unless hypothyroidism
develops. The management of Hashimoto's thyroiditis in children
and adolescents is exactly the same as in adults. With time, the
thyroid will become smaller though this may take several years.
In Hashimoto's thyroiditis, thyroid hormone secretion may be normal
at diagnosis. Careful monitoring at approximately 6 month intervals
is recommended in case hypothyroidism develops. Treatment with thyroid
hormone, once started, is taken for life. There are special groups
of children, such as those with Diabetes Mellitus, Down Syndrome,
or Turner Syndrome, who should be regularly checked, as they are
more likely to develop Hashimoto's thyroiditis.
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Graves'
Disease (Hyperthyroidism)
Graves' Disease, the
most common cause of hyperthyroidism in children, increases in frequency
as adolescence approaches. Development of eye complications (ophthalmopathy)
occurs, but is not nearly as severe as in adults. Children can have
the same symptoms as adults, but the child may not actually complain
about them. The biggest problem before the diagnosis is known, may
be extreme restlessness and short attention span, leading to school
difficulties and often parental exasperation. Treatment is usually
started with antithyroid drugs. Some children are best managed by
removing the thyroid gland once the hyperthyroidism is under control.
In other children long term use of the antithyroid drugs is best.
Treatment with radioactive iodine is only occasionally used in early
childhood. It may be very helpful in older adolescents, particularly
those whose hyperthyroidism is difficult to control.
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Other
Thyroid Disorders
Single thyroid nodules,
multinodular goitre, subacute thyroiditis, and other thyroid
disorders occur but are uncommon in Canadian children.
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Thyroid
Disease and Growth
Hypothyroidism in babies
is usually detected by neonatal screening, and treatment is instituted
promptly. If left untreated, it is associated with defects in growth
and development as described earlier in the section on congenital
hypothyroidism.
Children with hypothyroidism
can have all the same symptoms as adults but the most striking change
may be short stature despite a normal or increased weight. Once
treated with thyroid hormone, "catch-up growth" is the rule. Puberty
may be delayed or occasionally advanced.
There is no change in
intelligence if hypothyroidism develops after two years of age.
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Treatment
In children and adolescents
receiving treatment for either hypo or hyperthyroidism, it is essential
that the tablets be taken regularly. The parents must supervise
the treatment, and a pill minder box can be a very helpful way to
monitor and train the child. Children do not always appreciate the
reasons for regular treatment, and threatening them with the consequences
of the disease does not seem to be helpful.
For those children with
hypothyroidism, particularly when it has been quite long standing,
a return to normal thyroid function may be associated with a marked
change in behaviour. This can result in school difficulties. Teachers
should be made aware of the child's problem and any ongoing medical
recommendations.
In the case of children
with Graves' Disease, the difficulties mainly occur before treatment
is started. However, if the medication is not taken regularly symptoms
of hyperthyroidism will reappear.
For more information
see also the Research Recommendations on Maternal Hypothyroidism
from the Endocrine Society Maternal
Hypothyroidism. |
Written
by Sonia R. Salisbury, M.D., F.R.C.P.(C), Associate Professor Dalhousie
University, Head Department of Endocrinology Izaak Walton Killam
Children's Hospital, Halifax, NS.
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A
printed version of this Health Guide is available to health care
professionals and the public. For more information call the National
Office or contact your local
chapter.
Production of
the printed version of this Health Guide was made possible through
partial funding assistance from Health Canada. The views expressed
herein are solely those of the authors and do not necessarily represent
the official policy of Health Canada. |
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