Webster's New World Medical Dictionary

thyroid hormone organification defect IIb
See 
Pendred syndrome.
thyroid scan
An image taken of a patient’s thyroid
gland after the patient swallows radioactive iodine or
technetium. The image shows the thyroid gland in
action as it accumulates radioactive material.
Thyroid scanning is used to determine how active
thyroid tissue is in manufacturing thyroid hormone.
This can help a physician determine whether inflam-
mation of the thyroid gland (thyroiditis) is present.
It can also show the presence and degree of overac-
tivity of the gland (hyperthyroidism). Thyroid scan-
ning is especially helpful in evaluating thyroid
nodules, particularly after a fine-needle aspiration
biopsy has failed to provide a diagnosis. A scan can
reveal whether a thyroid nodule is functioning. A
functioning nodule actively takes up iodine to pro-
duce thyroid hormone, and so it produces a local-
ized “hot” area on the image. A nonfunctioning
nodule does not take up iodine, and it produces a
localized “cold” area. Most nodules, particularly if
they are functioning, are not malignant.
thyroid-stimulating hormone
A hormone that
is produced by the pituitary gland at the base of the
brain in response to signals from the hypothalamus
gland in the brain. Abbreviated TSH. TSH promotes
the growth of the thyroid gland in the neck and stim-
ulates it to produce more thyroid hormones. When
the amount of thyroid hormones is excessive, the
pituitary gland stops producing TSH, thus reducing
thyroid hormone production. This mechanism main-
tains a relatively constant level of thyroid hormones
circulating in the blood. Also known as thyrotropin.
thrombosis, deep vein
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