Hyperthyroidism
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In this condition the level of thyroid hormone is abnormally high.
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Types and clinical signs
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There are many causes of hyperthyroidism, most of which are environmental and a
small proportion of which are genetic. The adult-onset cases are usually caused
by non-genetic factors such as inflammation of the thyroid gland or other environmental
causes. Out of all the women with hyperthyroidism, it is important to identify those
with Graves- disease, the characteristic clinical sign of which is exophthalmos
- bulging eyeballs. In this disease, there are antibodies against the thyroid gland.
These antibodies can be detected by a blood test. In pregnant women, the antibodies
can pass to the fetus through the placenta and affect the fetus-s thyroid gland.
This can manifest in congenital
hypothyroidism which can cause mental retardation if left untreated. Treatment
should commence immediately after birth in order to prevent this. The drugs that
a woman with hyperthyroidism takes can also affect the fetus.
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Inheritance pattern
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In the hereditary types, this is usually multifactorial.
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Penetrance
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Partial.
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Associated features that can be demonstrated in tests performed during pregnancy
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There are usually no defects. If the hormonal deficiency is part of a syndrome,
there may be additional findings.
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What is the risk of recurrence in a subsequent pregnancy?
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The risk that the parents of a child with hyperthyroidism will have another affected
child depends on the cause and the exact type of the disease.
The risk of recurrence is determined within
genetic counseling after reviewing all the data.
In the adult-onset types, the risk of recurrence also depends on the cause.
Usually relatives are at risk of developing this type of hyperthyroidism, which
is non-congenital, but not to the extent seen in the congenital form.
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Molecular genetic information
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The gene for the disease
In most cases, the gene is unknown. If the exact enzyme deficiency causing the hyperthyroidism
is identified, then the gene can also be identified.
Location
Depends on the gene if the cause is genetic.
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Genetic testing
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Diagnostic testing
The disease is diagnosed by a blood test to measure the level of the thyroid hormone
and the levels of the hormones that regulate its activity: TSH and TRH. Additional
tests can also be performed, such as mapping of the thyroid gland, etc.
Carrier testing
At the present time, carrier testing is not possible in most cases. It depends on
the type of disease and whether the basic enzyme deficiency has already been identified.
Fetal testing
This is not necessary.
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Hyperthyroidism
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