Adam Borowski 2002 |
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Introduction /
Anatomy / Development
/ Cytology / Hormones
/
Clinical
CLINICAL
Hyposecretion
or hypersecretion of the thyroid hormones produces a variety of clinical
abnormalities.
Hyposecretion
of Thyroid Hormones
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In the
majority of circumstances, thyroid hyposecretion occurs due to
defects in the thyroid gland itself.
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However in
some cases the defect can occur in the hypothalamus or pituitary,
resulting in a deficiency in TSH production.
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Due to a
slower metabolic rate and reduced heat production, hypothyroid
individuals cannot tolerate cold temperatures.
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Water
accumulates in the skin, leading to a condition called myxedema, in
which the skin has a thickened, puffy appearance (the image below
shows the skin of someone suffering from myxedema).
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The heart
rate and strength of cardiac contractions are reduced, contributing
to a reduction in cardiac output.
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Additionally
there is a slowing of interlectual functions, leading to lethargy
and a degree of speech impairment.
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Hypothyroidism
during fetal development can lead to cretinism.
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This results
as thyroid hormones are responsible for the development of the
nervous system.
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Sufferers
have mental impairment and often suffer from dwarfism as their
linear growth is affected.
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The patient
in the image below is suffering from cretinism.
Hypersecretion
of Thyroid Hormones
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Hyperthyroid
individuals exhibit a markedly increased heart rate, an
insensitivity to heat, charcteristic protruding eyeballs and
considerable weight loss due to the protein-catabolic effects of
excess thyroid hormones.
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One of the
most common forms of hyperthyroidism is Grave's Disease.
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This
condition arises from an immune system abnormality.
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Antibodies
are produced against the thyroid follicle cell causing activation of
the TSH receptor and a subsequent increase in thyroid hormone
production.
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Often a
goiter (enlargement of the thyoid) will form as a result of the TSH-like
effects of the autoantibodies.
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The images
below show patients suffering from Grave's Disease and a goiter.
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