Goiter journal 1.docx

7/24/2019 Goiter journal 1.docx

1/3

BackgroundIn 1656, Thomas Wharton described the distinct nature of what he termed the thyroid gland,

distinguishing it from the larynx, as this structure had been considered a laryngeal gland from the

time of Andreas Vesalius in the 16th century. It was nearly !! more years before the function ofthe thyroid was elucidated. The normal adult thyroid gland weighs 1!"5 g and has lobes

connected by an isthmus. #early 5!$ of thyroid glands exhibit a %yramidal lobe arising from thecenter of the isthmus. &ongitudinal dimensions of the lobes of the thyroid range u% to 5 cm, as

shown in the image below.

Thyroid nuclear scan of a %atient with a euthyroid goitershowing different %ro'ections.

A goiter is an enlarged thyroid gland, and it may be diffuse or nodular. A goiter may extend into

the retrosternal s%ace, with or without substantial anterior enlargement. (ecause of the anatomic

relationshi% of the thyroid gland to the trachea, larynx, su%erior and inferior laryngeal ner)es,and eso%hagus, abnormal growth may cause a )ariety of com%ressi)e syndromes. Thyroid

function may be normal *nontoxic goiter+, o)eracti)e *toxic goiter+, or underacti)e *hy%othyroid

goiter+.

Pathophysiology

The thyroid gland is controlled by thyroid"stimulating hormone *T- also /nown as

thyrotro%in+, secreted from the %ituitary gland, which in turn is influenced by the thyrotro%in"releasing hormone *T0-+ from the hy%othalamus. T- %ermits growth, cellular differentiation,

and thyroid hormone %roduction and secretion by the thyroid gland. Thyrotro%in acts on T-

rece%tors located on the thyroid gland. Thyroid hormones are synthesied from iodination oftyrosine. The iodine is trans%orted from %lasma into the thyroid cell )ia a sodium"iodide

sym%orter. This is an acti)e %rocess resulting in an intracellular iodine le)el exceeding ! times

the %lasma iodine le)el. This iodine trans%ort acti)ity is controlled by T-.213 erum thyroid


2/3

hormones le)othyroxine and triiodothyronine feed bac/ to the %ituitary, regulating T-

%roduction. Interference with this T0-"T- thyroid hormone axis causes changes in the

function and structure of the thyroid gland. timulation of the T- rece%tors of the thyroid byT-,T-"rece%tor antibodies, or T- rece%tor agonists, such as chorionic gonadotro%in, may

result in a diffuse goiter. When a small grou% of thyroid cells, inflammatory cells, or malignant

cells metastatic to the thyroid is in)ol)ed, a thyroid nodule may de)elo%.

A deficiency in thyroid hormone synthesis or inta/e leads to increased T- %roduction.Increased T- causes increased cellularity and hy%er%lasia of the thyroid gland in an attem%t to

normalie thyroid hormone le)els. If this %rocess is sustained, a goiter is established. 4auses of

thyroid hormone deficiency include inborn errors of thyroid hormone synthesis, iodinedeficiency,23 and goitrogens.

A goiter may result from a number of T- rece%tor agonists. T- rece%tor stimulators include

T- rece%tor antibodies, %ituitary resistance to thyroid hormone, adenomas of the hy%othalamus

or %ituitary gland, and tumors %roducing human chorionic gonadotro%in.

EpidemiologyFrequency

United States

Autopsy studies suggest a frequency of greater than 50% for thyroid nodules; with high-resolutionultrasonography the !alue approaches "0% of patients with nonthyroidal illness# $n the ickham study fromthe &nited 'ingdom ()% of the population had a goiter#*+, $n the ramingham study ultrasonography re!ealedthat +% of men older than )0 years had thyroid nodules while +)% of women aged ".-5/ years had thyroidnodules#*", $n the &nited tates most goiters are due to autoimmune thyroiditis 1ie 2ashimoto disease3#

4he incidence of thyroid cancer has een rising worldwide# 4he reasons are unclear ut this trend may erelated to etter detection and diagnostic methods#*5,

International

orldwide the most common cause of goiter is iodine deficiency#*6, $t is estimated that goiters affect as many as600 million of the /00 million people who ha!e a diet deficient in iodine#

$n a 7erman study )+5 people underwent ultrasonographic thyroid screening as well as asal 42measurement during a pre!enti!e-health checkup# *), 4hyroid nodules were detected in "+6 1)/%3 of thepersons screened; in a pre!ious 7erman study ultrasonographic screening of more than .0000 peopledetected thyroid nodules in ++% of the normal population# 4he authors of the latter report attriuted thisdifference to the fact that patients in their study were screened using (+ 829 ultrasonographic scanners whichwere more sensiti!e than the :#5 829 scanners used in the pre!ious study# According to the in!estigators theirresults indicated that the question of routine iodine supplementation requires renewed attention#

Mortality/Morbidity

8ost goiters are enign causing only cosmetic disfigurement# 8oridity or mortality may result fromcompression of surrounding structures thyroid cancer hyperthyroidism or hypothyroidism#

Race

o racial predilection e


3/3

$n the ickham study 6)% of women had a goiter compared to :% of men#*+,

4hyroid nodules are less frequent in men than in women ut when found they are more likely to e

malignant#

Age

4he frequency of goiters decreases with ad!ancing age# 4he decrease in frequency differs from the incidenceof thyroid nodules which increases with ad!ancing age#

James R Mulinda, MD, FAC>onsulting taff ?epartment of Endocrinology Endocrinology Associates $nc

Source: http://emedicine.medscape.com/article/120034-overview#showall

Documents

Goiter journal 1.docx