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Congenital Hypothyroidism pamphlet
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CONGENITAL
HYPOTHYROIDISM
An Information Guide for
Parents
Based on the publication by Education Resource Centre,
Royal Children’s Hospital, March 1987
John C Coakley M.D., John F Connelly M.D
Department of Clinical Biochemistry
Royal Children’s Hospital
Parkville, Victoria, Australia
INTRODUCTION: the thyroid gland and the different
types of hypothyroidism. The
In the past, children born with optimistic outlook that can be
Congenital Hypothyroidism often had expected with early treatment is also
serious problems because of late explained. In addition, information is
diagnosis. With the introduction of given about the Newborn Thyroid
Newborn Screening in 1977, the Screening Program and how it
outlook for these children changed operates. In the final section of the
dramatically and they now lead normal, booklet, we answer some of the
healthy lives. common questions that parents ask
concerning Congenital
This booklet has been written to help Hypothyroidism.
your understanding of Congenital
Hypothyroidism, and we hope that you GLOSSARY OF TERMS:
will find it useful and reassuring.
Each year in South Australia, First, let us begin by defining some of
approximately 8 babies are born with the terms that we will be using in this
Congenital Hypothyroidism. There is booklet. The definitions are arranged
usually no indication that there is alphabetically.
anything medically wrong with these
AGENESIS: When there is agenesis
babies at the time of birth. Therefore, it
of an organ in the body, this means
often comes as a great shock to you,
that the organ is absent.
the parents, to be told that your baby
has a thyroid gland which is not ATHYROSIS (sometimes spelt
functioning properly, and it may be ATHYREOSIS): Absence of the
difficult for you at first to absorb all the thyroid gland.
information that you are given
regarding hypothyroidism. CONGENITAL: Present at birth.
Therefore, we have written this booklet DYSHORMONOGENESIS:
so that you may learn about the Disturbance in the production of a
condition of congenital hypothyroidism hormone.
more easily. These pages contain
information regarding the function of ECTOPIC: Out of its normal position.
ENDOCRINE SYSTEM: A Hypothyroidism that happens the element iodine, and this is
system of glands in the body because of failure of the why iodine is an essential part
which secrete substances function of the pituitary gland. of our diet.
called hormones into the
THYROID GLAND: An The pituitary gland which is
bloodstream. Some of the
endocrine gland which situated at the base of the brain
endocrine glands include the
produces the hormone called controls the thyroid. The
thyroid, pituitary, the ovaries
thyroxine. The thyroid is pituitary manufactures a
and the testicles.
situated in the neck, as hormone called thyroid
ENZYME: A special protein illustrated below. stimulating hormone (TSH) or
which is formed in a living cell thyrotropin. When the thyroid
and which is an essential gland is producing too little
element for a particular thyroxine, the pituitary is able to
chemical reaction taking place sense this. As a result, it
in that cell. increases its output of thyroid
stimulating hormone which
GOITRE: A visible swelling of
circulates in the blood to the
the thyroid gland in front of the
thyroid gland and stimulates it
neck.
to produce more thyroxine. If,
HORMONE: A chemical on the other hand, the thyroid is
substance which is made by an secreting too much thyroxine,
endocrine gland and then THYROID STIMULATING the pituitary cuts back its
secreted into the bloodstream. HORMONE (abbreviation secretion of thyroid stimulating
There are a large number of TSH): A hormone which is hormone.
hormones which produce produced by the pituitary gland Therefore, when the thyroid
widespread effects on the body. and which stimulates the gland is under-active, the blood
HYPOTHYROIDISM: A thyroid gland to secrete will contain a low level of the
disease in which the thyroid thyroxine. An alternative name hormone, thyroxine, and a high
gland is under-active. The term for TSH is thyrotropin. level of the thyroid stimulating
Congenital Hypothyroidism THYROXINE: The hormone hormone.
means that the underactivity of produced by the thyroid gland. The concepts we have just
the thyroid gland is present at The tablets given to treat described are illustrated in the
and before the time of birth. hypothyroidism contain this diagram below.
JAUNDICE: A yellow colouring hormone and are called
of the skin produced by an thyroxine tablets.
excessive amount of the
pigment bilirubin. Bilirubin THE DEVELOPMENT,
comes from the breakdown of FUNCTION AND CONTROL
red blood cells. OF THE THYROID GLAND
METABOLISM: The activity The thyroid gland begins to
carried on by each cell in the form very early in the
body in which foodstuffs are developing human embryo –
broken down and energy about three weeks after ACTIONS OF THYROXINE
produced. conception. It develops first in AND CONSEQUENCES OF
the region where the mouth and LACK OF THYROXINE
NEONATE: A baby less than
one month of age. tongue will form, and then it
migrates downwards into the Thyroxine is an extremely
PITUITARY GLAND: An neck to take up its final position important hormone for normal
endocrine gland which is about towards the base of the neck in growth and development. It
the size of a marble and is front and on each side of the exerts control over the body’s
situated at the base of the trachea or windpipe. Very soon metabolism, so that when there
brain. This gland is very after it begins to develop, the is not enough thyroxine, cell
important because it controls thyroid gland consists of two activity (metabolism) slows
the other endocrine glands, lobes (see illustration above). down, and when there is too
including the thyroid. The function of the thyroid much, it speeds up. Slow body
gland is to manufacture metabolism may bring about
PRIMARY the following effects:
HYPOTHYROIDISM: thyroxine and secrete it into the
Hypothyroidism due to disease bloodstream. This hormone is 1. Sluggishness in both
of the thyroid gland itself. made in a number of steps, for physical and mental activity.
each of which a particular
SECONDARY protein called an enzyme is 2. Low body temperature and
HYPOTHYROIDISM: necessary. Thyroxine contains low pulse rate.
3. Intolerance of cold 1. Those with an absent 3. Those with a malformed
weather. thyroid gland (Athyrosis) thyroid gland in the normal
position
4. Constipation. In this group, the thyroid gland
has failed to develop before This condition is sometimes
These effects may be seen at
birth. The gland is absent and called thyroid hypoplasia and it
all ages. In earlylife, there are
will never grow. Consequently only accounts for a very small
additional consequences of
no thyroxine is produced. This percentage of the total number
lack of thyroid hormone.
condition is called thyroid of cases. In thyroid hypoplasia,
Babies with Congenital
agenesis or athyrosis. It is the gland is small, poorly
Hypothyroidism have the
more common in females formed and occasionally
following features:
compared to males – about consists of only one lobe.
1. Slowness of Growth twice as many girls as boys are
4. Those who have a thyroid
affected. It occurs about once
While thyroxine appears not to gland which has developed
every 10,000 births and
be necessary for growth before normally, but which cannot
accounts for about 35% of the
birth, it is essential for normal produce normal amount of
cases detected by Newborn
growth after birth. If a baby has thyroxine
Screening. The reason why the
an untreated thyroid deficiency, thyroid gland fails to develop in This condition is known as
he or she will remain small these babies is presently thyroid dyshormonogenesis
through infancy and childhood unknown. However, research and it accounts for about 15%
and end up being very short. into the condition suggests that of the cases detected by
This slowness of growth affects one of a cascade of genes Neonatal Screening.
all parts of the body, including involved in forming the thyroid Dyshormonogenesis (enzyme
the skeleton. gland is not turned on at the defects) can be either transient,
2. Slowness of Mental right time. in which case it gets better with
Development the passage of time, or else it is
2. Those with an ectopic
permanent and lasts for life. In
Intellectual retardation can thyroid gland
babies affected with
occur with lack of thyroxine. In these babies, the thyroid is dyshormonogenesis, the thyroid
The degree of retardation is small and poorly formed and gland is often enlarged and
dependent upon the severity of does not occupy its normal may be seen or felt in the front
the deficiency of the thyroid position in the neck. It is often of the neck as a goitre. We will
hormone. When there is only a found at the base of the tongue, now explain in more detail its
partial lack of thyroxine, little near the place where the gland underlying causes.
deterioration in mental function first began to form in the
may occur. When thyroxine is Firstly let us consider
embryo. An ectopic thyroid
completely absent and the baby permanent
may have varying degrees of
receives no treatment, mental dyshormonogenesis. You will
function. Sometimes it is very
retardation may be severe. recall that the thyroid hormone,
small and under-active. On
However, this will not occur if thyroxine, is made in a number
other occasions, it is able to
treatment is begun early. (See of steps, each controlled by a
produce a nearly normal
section on Outlook for Babies particular enzyme. In very rare
amount of thyroid hormone.
with Permanent Congenital circumstances, one of these
Thus there is a spectrum of
Hypothyroidism). enzymes is missing, and this
severity in this condition. We
causes permanent problems
3. Persistent Jaundice know that after birth an ectopic
making thyroxine. This
thyroid gland will not become
As defined in the glossary, the abnormality is an inherited
bigger or descend to its normal
term jaundice means that the condition and therefore other
position. In fact, its function will
skin has a yellow colour due to babies born in to the family are
often deteriorate further with
the presence of the pigment at risk of having it. Usually the
the passage of time.
bilirubin. It is common for likelihood of another child
newborn babies to have Ectopic thyroid glands also having thyroid
jaundice which may last for a occur about twice as frequently dyshormonogenesis due to an
week or two. In untreated in girls as in boys. They enzyme defect is one in four.
hypothyroidism, jaundice may account for about 50% of the Boys and girls are equally
persist for much longer than cases detected by Newborn affected.
this. Screening and so are slightly
With transient
more common than the cases
dyshormonogenesis, the
TYPES OF CONGENITAL of thyroid agenesis. Again, we
function of the thyroid returns to
HYPOTHYROIDISM do not know for sure why in
normal after a variable period of
some babies the thyroid gland
time. There may be a number
We can divide patients with remains in an ectopic position,
of causes of this problem. On
Congenital Primary but the same factors that cause
very rare occasions, antibodies
Hypothyroidism into four thyroid agenesis may well give
from the mother’s blood cross
groups, as follows: rise to this problem.
the placenta during the
pregnancy and decrease the birth. They take some time, carried out after two or three
function of the baby’s thyroid months in fact, to develop. years treatment in order to
gland. Another cause is the Therefore, if Newborn determine if an enzyme
presence of too much iodine in Screening is not carried out, deficiency is present.
the body. You may remember most cases of hypothyroidism
that we stated in a previous will be missed at birth and TREATMENT
section that the element iodine treatment delayed.
is essential for the manufacture In hypothyroidism, the thyroid
2. Congenital hypothyroidism is
of thyroxine. However, too gland is unable to make
a relatively common condition.
much iodine can also bring enough thyroxine for the body’s
About 8 new cases are
about a decrease in the needs, and therefore this
diagnosed in South Australia
function of the thyroid gland. A hormone must be replaced. It
each year (one in 3,500 births).
baby may be at risk of is given in tablet form by mouth.
becoming hypothyroid if the 3. With early diagnosis and The thyroxine that is present in
mother takes a lot of iodine- treatment, it can be confidently the tablets is exactly the same
containing medication during expected that even severely as the thyroxine that is naturally
pregnancy and/or while breast affected infants will develop present in the body. Thyroxine
feeding. Once, however, the normally both physically and is now made by chemical
excessive iodine intake stops, mentally. means, previously it was
the thyroid gland will return to extracted from the thyroid
normal and the baby will not INVESTIGATION TO glands of animals.
suffer any long-term ill effects. DETERMINE THE TYPE OF
Thyroxine is well absorbed from
In a few cases of thyroid HYPOTHYROIDISM
the digestive tract and readily
dyshormonogenesis, both enters the bloodstream. It does
permanent and transient, we When a baby is found to have
not have to be given by
are unable to find out exactly abnormal results on screening,
injection, like some other
the precise cause of the this information is immediately
hormones, such as insulin
trouble. conveyed to his/her doctor or
(used for the treatment of
midwife. They then arrange for
diabetes).
the baby to be seen within a
NEWBORN SCREENING
short period of time either by All human beings require
themselves or by another vitamins in their diet because
All babies in Australia are
specialist. At this visit, a their bodies are unable to make
screened for Congenital
medical history is taken from them. One can look upon the
Hypothyroidism. This
the parents and the baby is treatment of hypothyroidism as
screening began in South
carefully examined in order to simply the taking of another
Australia in 1977. About two
gain clues as to what type of “vitamin”, which in this
days after birth, a small amount
hypothyroidism is present. particular circumstance, the
of blood is taken from the
body is unable to manufacture.
baby’s heel, placed on a piece At the first visit, a blood test is
of filter paper and forwarded to done in order to confirm the The amount of thyroxine that is
a central laboratory for assay. results obtained by Screening. given depends upon a number
Babies with all four categories of factors, including the size of
of Congenital Hypothyroidism The other investigation that is
the patient. Naturally, as the
will be identified because they performed at this time is called
baby grows, a bigger dose will
will have high levels of thyroid a thyroid scan. For this test,
be needed. Once treatment
stimulating hormone. the baby is given an injection of
has been started, blood tests
a radioactive substance called
are done at regular intervals in
Babies who have technetium which is taken up
order to measure the
hypothyroidism as part of a by the thyroid gland. Thus it is
concentration of the thyroid
pituitary gland problem will possible to see the position and
hormone in the blood. These
have low or undetectable levels shape of the thyroid and see if
tests are usually done every
of TSH and will NOT be the gland is absent, ectopic or
three months for the first three
identified by the Screening present in the normal position.
years of life, four monthly till
Program. There is virtually no risk
age seven then six monthly
associated with the use of
The reason why Newborn thereafter. We aim to keep the
technetium because only a low
Screening is carried out are as thyroxine level in the blood
dose is used and its
follows: about the upper limit of normal.
radioactivity goes away within
With appropriate treatment, the
1. It is very difficult to diagnose hours. A thyroid scan can only
stimulus to the pituitary gland to
Congenital Hypothyroidism at be performed when the baby is
secrete large amounts of
birth, just by examining the not on treatment. This is why it
thyroid stimulating hormone will
baby. Some of the features is usually done at the first visit.
no longer be present.
described previously e.g. slow
In some babies with thyroid Therefore, the level of this
growth and impaired mental
dyshormonogenesis, more hormone in the blood will be
development are not present at
detailed investigations are suppressed, but it may take
several months for this to have normal intelligence and effects occur if the dosage is
occur. are healthy in every respect. appropriate. If, however, too
much thyroxine is given, the
If treatment is inadequate, e.g. It should also be appreciated
effects will be the same as
if the dosage is too low or the that, just there is a range of
those that occur with an
tablets are not being given levels of intelligence in the
overactive thyroid gland, viz.,
properly, the thyroxine general community, so there is
rapid pulse, loss of weight,
concentration in the blood will a range of intellectual abilities
restlessness, overactivity, etc.
be low and there will be an amongst the hypothyroid
elevated level of the thyroid children. Whilst the majority of Q. What are the risks of a
stimulating hormone. The baby them are about average in further child in the family
or child may be drowsy or tired. mental skills, some are a lot having hypothyroidism?
Treatment for permanent below this and some above it.
A. The risks depend on the
hypothyroidism is life-long. If In addition, a small proportion
cause. Most cases of
the tablets are ceased for a of the children with
Congenital Hypothyroidism are
prolonged time, the symptoms hypothyroidism have other
due to absent, ectopic or
already described will return. medical problems which may
hypoplastic thyroid glands.
also have an effect on their
These problems are not
FOLLOW-UP intelligence.
inherited and the risk of a
subsequent child having a
Babies with Congenital QUESTIONS AND ANSWERS
similar condition is very small.
Hypothyroidism are reviewed at The likelihood of a baby being
regular intervals to assess their Q. What will happen if my born with an absent or
progress. Your doctor will want baby misses a dose of malformed thyroid gland in the
to make sure that the thyroxine or vomits up one of general population is about one
appropriate dosage of thyroxine the tablets? in 3000. This risk may be
is beingprescribed and that slightly higher when there is
A. No harm is done if only one
there are no signs of under or already one affected child in the
or two doses of thyroxine are
over treatment. Usually very
missed. It is, of course, family, but it is not a substantial
few problems are encountered risk. In the South Australian
important that the tablets are
once therapy has commenced. follow-up program, there are
administered regularly, so
In addition, with the agreement make sure that you obtain a now over 100 families with
of the parents and doctor, all repeat prescription from your children having either absent,
hypothyroid babies so far doctor when your supplies are ectopic or hypoplastic thyroid
identified by screening in South getting low. glands, but in only one family is
Australia have taken part in a there more than one affected
Q. Can treatment be stopped child.
follow-up program at the
at any stage, e.g. on reaching
Women’s and Children’s
adult life? In the few cases of permanent
Hospital. After excellent dyshormonogenesis due to an
outcomes from the first 22 A. In permanent Congenital enzyme deficiency, the risk of
years of Newborn Screened Hypothyroidism, it is not having a second infant with the
and treated children with possible to stop treatment. same problem is one in four
Congenital Hypothyroidism, we Thyroxine must be taken (see section Types of
no longer perform psychometric regularly throughout life, even Congenital Hypothyroidism).
tests routinely. when physical growth has With transient
ceased. dyshormonogenesis, there is
OUTLOOK FOR BABIES usually no risk of recurrence,
WITH PERMANENT unless the cause of the
CONGENITAL Q. Will any problems occur
when my child has problem, e.g. excess iodine, is
HYPOTHYROIDISM still present.
immunisations or has to take
Before the Newborn Screening other medication? Q. When a person with
Program for hypothyroidism A. No. Children with hypothyroidism has children
was instituted, the diagnosis hypothyroidism can have of his or her own, what risk
was usually delayed, and as a do the children face of
result, some babies suffered the usual immunisations and having the same condition?
permanent mental retardation. take other medication without
any problem. A. There is only a low risk that
With early diagnosis, this can the children of a congenitally
be prevented. From the follow- Q. What are the side effects hypothyroid mother or father
up studies being undertaken at of thyroxine treatment? will have the same problem. In
the Women’s and Children’s general, this applies to all the
Hospital and around the world, A. Because the treatment of
hypothyroidism involves types of Congenital
we have found that just about Hypothyroidism. Even with
all babies and children whose replacement therapy with a
natural hormone, no side permanent dyshormonogenesis
only problem is hypothyroidism due to an enzyme deficiency,
the risk remains low, unless the
affected person happens to
marry someone who either has
the same condition or is a
carrier of it.
Q. Is a child with
hypothyroidism more likely to
get other diseases later in life?
A. No. With regard to the risk
of contracting other disease
later in life, hypothyroid children
are no different from the normal
population.
CONCULSION
By reading this booklet, we
hope that you have gained a
better understanding of
congenital hypothyroidism.
Because of Newborn
Screening, babies who are born
with a thyroid problem today
can be expected to grow up
normally, just like other healthy
children who possess a normal
thyroid gland. We can
confidently predict that your
child with hypothyroidism will
become a healthy adult and a
productive member of the
community.
The doctor looking after your
child will always be available to
discuss any further queries or
concerns that you might have
about the condition.
Updated January 2007
