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Thyroid and Parathyroid Glands 263
Nonneoplastic Diseases of the Thyroid Gland
Congenital Anomalies
Lingual thyroid
Lingual thyroid occurs when the thyroid gland fails to descend to its
normal cervical location. Approximately 1 in 600,000 live births pres-
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ent in childhood or adolescence with lingual thyroid. In cases of unde-
scended thyroid, 90% were found within the tongue and 10% in the
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anterior neck above the hyoid bone. The posterior part of the tongue
around the foramen caecum is the most common site of lingual thyroid.
It is most common in females. Symptoms usually consist of dysphagia Figure 40.1: A ten-year-old boy with endemic multinodular goiter.
and dyspnea. Diagnosis is confirmed by radioactive iodine scintigra-
phy. Of patients with lingual thyroids, 75% have no functional thyroid staple foods in the tropics, namely, cassava, maize, bamboo shoots,
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tissue. Therefore, testing for location of thyroid tissue in addition to and sweet potatoes. The brassica family of vegetables is a well-known
gland function is necessary. example producing thioglycosides. Flavonoides from millet, a staple
Treatment consists of complete excision of the lingual thyroid food in Sudan, are also known to have antithyroid activity.
followed by lifelong thyroid hormone therapy. Autotransplantation Congenital goiter
of the excised lingual gland or pedicle transfer—retaining a vascular
The majority of neonatal goiters result from maternal ingestion of goi-
pedicle and moving part of the thyroid into the neck—has been
successful in several cases. 8,10 trogens. In the newborn infant, the most commonly implicated drugs
are iodides and thiourea derivatives used for treatment of maternal
Goiters thyrotoxicosis. Congenital goiter has also been described in a newborn
An enlarged thyroid gland due to any cause is called a goiter. Goiters with Prader-Willi syndrome. Most goiters in the newborn are of the
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are classified as diffusely enlarged or nodular and either toxic or hyperplastic type and disappear a few weeks after birth. 16
euthyroid. A diffuse thyroid enlargement is the most common form of Ultrasonography provides a useful noninvasive investigation in
goiter in small children. Physiologically, diffuse thyroid enlargement assessing the size of the goiter as well as the response to therapy.
may be related to autoimmune diseases, or can be an inflammatory or Rarely, goiters may be large enough to produce severe respiratory
compensatory response. In a study of 152 school children with goiters, distress by tracheal compression. These patients may require division of
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most patients (83%) had adolescent colloid goiter. Goiters may be the isthmus or subtotal thyroidectomy to relieve tracheal compression.
endemic or sporadic.
Physiologic goiter
Endemic goiters In physiological states such as puberty, menstruation, and pregnancy or
Endemic goiters exist when more than 10% of any community has lactation, the body’s requirement for thyroid hormones is increased due
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goiters, usually in high rocky mountain regions of the world. Endemic to the increased metabolic activity. If this requirement is not met, TSH
goiter has been described in nearly all African countries. Endemic secretion is increased to stimulate the thyroid. The thyroid gland under-
goiter is mainly caused by insufficient iodine intake in the diet. The goes physiological hyperplasia and may therefore enlarge. The thyroid
iodine content of the water supply and the soil in granite mountain gland is enlarged evenly, and feels comparatively soft. This occurs at
regions are very low. Other causes of endemic goiter are goitrogens in puberty and is almost exclusively confined to females. Involution takes
food and excessive calcium salts in the water supply. Cassava, which place when the hormones are increased in a sufficient amount or the
is a common foodstuff in most African communities, contains cyano- need for an increased amount is over, usually by the twenty-first year. 6,12
genic glycosides, which yields thiocyanate as a metabolic by-product. Colloid goiter
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Thiocyanate inhibits iodine uptake by the thyroid.
The physiologic changes to iodine deficiency are usually Colloid goiter is diffuse hyperplasia of the thyroid gland due to iodine
accompanied by an increase in the size of the thyroid gland. Generalised deficiency. It is commonly seen in endemic areas but may also occur
epithelial hyperplasia occurs, with cellular hypertrophy and reduction sporadically. In endemic areas, children may be affected, but girls from
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in follicular spaces. In chronic iodine deficiency, the follicles become puberty to 20 years of age are most commonly involved. The gland is
inactive and distended with colloid accumulation. These changes enlarged, smooth-surfaced, may be firm in areas and soft in others, and
persist into adulthood, and focal nodular hyperplasia may develop, has some degree of elasticity. All goiters of puberty that do not subside
leading to nodular formation. Some of these nodules retain the ability completely must be considered colloid goiters. The gland may occa-
to secrete thyroxin and form functioning thyroid nodules. Others do sionally be big enough to cause tracheal compression. The degree of
not retain this ability, become inactive and form cold nodules. Necrosis lateral lobe enlargement determines the extent of displacement or nar-
and scarring result in fibrous setae, which contribute to the formation rowing of the trachea. Spontaneous regression is common, although, on
of multinodular goiters (Figure 40.1). Some multinodular goiters occasion, minimal amounts of thyroxine preparation may be necessary.
eventually become toxic. One study reports an increasing risk of Classification of goiter in general is according to the size of
toxicity developing in nodular goiters in children and adults in Africa, the thyroid gland on physical examination and the grading system
and 10.7% of adult nodular goiters may develop infective thyroiditis recommended by the World Health Organization (WHO) in 1960 and
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(thyroid abscess), although whether this infective complication occurs modified in 1994:
in children is not clear. 13,14 • Grade 0: No palpable or visible goiter
Sporadic goiters • Grade 1: Mass consistent with enlarged thyroid that is palpable but
Sporadic goiters occur in areas where goiters are not endemic. Sporadic not visible when the neck is in the neutral position; it also moves
goiters affect relatively few people and are usually pathological. The upwards in the neck as the subject swallows.
persistence of goiters in some areas with adequate iodine prophy- • Grade 2: Swelling visible in a neutral position of the neck and con-
laxis and the unequal geographic distribution of goiters in iodine- sistent with an enlarged thyroid when the neck is palpated.
deficient areas suggest the existence of other goitrogenic factors.
Cyanoglucosides are naturally occurring goitrogens found in several