CONGENITAL HYPOTHYROIDISM
As you know a small blood sample for chemical testing was taken from
your baby (usually by a heel prick with the blood spotted onto a card)
between the sixth to tenth days of life. The tests on that sample have
shown that your child may have congenital hypothyroidism. This is a condition
in which there is underactivity of the thyroid gland (hypothyroidism) present
at the time birth (congenital).
The thyroid gland lies in the front of the neck across the upper part
of the trachea (windpipe). Its main function is to produce and transfer
into the blood a chemical (hormone) called thyroxine. After birth (but
fortunately only to a much lesser extent before birth) this hormone has
an important role in regulating the growth and development and the chemical
activity of nearly all the cells in the body, including the brain. Lack
of thyroxine causes slowing of these processes. It is essential at all
times of life but particularly in the growing child.
Cause.
For reasons which are understood in only a few cases, in about 1 child
in 3,500 the thyroid gland either fails to develop properly before birth
or fails to work adequately. This is seldom apparent from the baby's physique
or behaviour until some weeks after birth but it is extremely important
to identify the problem early because if it remains undetected and untreated
there is slowing of the development of all organ systems including the
brain. If thyroxine is not given within the first few weeks after birth
brain damage can occur. For this reason all babies are now tested for this
condition. If the screening test shows any indication of underactivity
thyroid function must be more accurately checked on a liquid blood sample.
If this confirms underactivity treatment with thyroxine is started immediately.
As long as the thyroxine is started within a few weeks of birth growth
and development is normal.
Treatment.
Thyroxine is made chemically and is available as small white tablets
(it is not possible to make a reliable liquid preparation) in 25, 50 and
100 microgramme (mcg) sizes. Most babies are started on a dose of 25-50
mcg a day. (A dose equivalent to 37.5mg a day can be given by giving 25
and 50 mcg on alternate days). The tablets are easily crushed and given
with some milk off a spoon. On treatment further blood samples are needed
to allow adjustment of the dose to produce a normal level of thyroxine
and the thyroid controlling hormone (TSH) in the blood. Frequent blood
tests are needed at first but these can be less frequent as the child grows
older. The dose of thyroxine needs to be increased as the child grows but
most adults need only 150-200mcg per day. Do not be misled by the small
size and unimpressive nature of the thyroxine tablets, this hormone is
absolutely essential for the normal growth and development of your child.
Establish a foolproof routine for giving the tablet daily. An occasional
missed tablet is inevitable and does not matter because thyroxine is slowly
used in the body, it is not necessary to give an extra one when the omission
is realised.
Rarely congenital hypothyroidism may prove to be transient and the function
of the gland may recover. If there is any doubt that lifelong thyroxine
treatment is needed a further check on the function of the gland can be
made. This requires stopping treatment briefly and is best done when the
child is a little older, usually after the age of two or three years. No
harm at all will have resulted from giving thyroxine up till then because
the natural secretion from the gland is adjusted to maintain a normal level.
Outlook.
On treatment the child with congenital hypothyroidism is entirely normal.
This is not a medication, it is simply an exact replacement of a missing
chemical. There is therefore no need to worry whether the child can have
normal immunisations, treatment needed for other conditions and so on,
nothing is barred. There is naturally a tendency to worry that quirks of
physique or behaviour may relate to the congenital hypothyroidism or its
treatment but be assured that as long as the thyroxine dose is appropriate,
they do not. |
