3. Epidemiology
International
Worldwide, the most common cause of goiter is iodine deficiency.
It is estimated that goiters affect as many as 200 million of the 800
million people who have a diet deficient in iodine.
Mortality/Morbidity
Most goiters are benign, causing only cosmetic disfigurement.
Morbidity or mortality may result from compression of surrounding
structures, thyroid cancer, hyperthyroidism, or hypothyroidism.
Sex
The female-to-male ratio is 4:1.
4. Pathophysiology
The thyroid gland is controlled by thyroid-stimulating
hormone (TSH; also known as thyrotropin), secreted
from the pituitary gland, which in turn is influenced
by the thyrotropin-releasing hormone (TRH) from
the hypothalamus. TSH permits growth, cellular
differentiation, and thyroid hormone production and
secretion by the thyroid gland.
A deficiency in thyroid hormone synthesis or intake
leads to increased TSH production. Increased TSH
causes increased cellularity and hyperplasia of the
thyroid gland in an attempt to normalize thyroid
hormone levels. If this process is sustained, a goiter
is established. Causes of thyroid hormone deficiency
include inborn errors of thyroid hormone synthesis,
iodine deficiency, and goitrogens.
5.
6. Clinical features
โข Goitres are present on examination in up to 9% of the
โข population.
โข Most commonly a goitre is noticed as a cosmetic defect by
the patient.
โข The majority are painless, but pain or discomfort can occur
in acute varieties.
โข Large goitres can produce dysphagia and difficulty in
breathing, implying oesophageal or tracheal compression.
7. โข A small goitre may be more easily visible (on
swallowing) than palpable.
โข Clinical examination should record the size,
shape, consistency and mobility of the gland
as well as whether its lower margin can be
demarcated (thus implying the absence of
retrosternal extension).
โข Examination should never omit an assessment
of the patientโs clinical thyroid status.
8. โข Specific enquiry should be made about any medication,
especially iodine-containing preparations, and possible
exposure to radiation.
Particular points of note are:
โ Puberty and pregnancy may produce a diffuse increase
in size of the thyroid.
โ Pain in a goitre may be caused by thyroiditis, bleeding
into a cyst or (rarely) a thyroid tumour.
โ Excessive doses of carbimazole or propylthiouracil will
induce goitre.
โ Iodine deficiency and dyshormonogenesis can also cause
goitre.
10. Diffuse goitre
โข Simple goitre
โข In this instance no clear cause is found for
enlargement of the thyroid, which is usually
smooth and soft. It may be associated with
thyroid growth-stimulating antibodies.
11. โข Autoimmune thyroid disease
โข Hashimotoโs thyroiditis and thyrotoxicosis are
both associated with firm diffuse goitre of
variable size. A bruit is often present in
thyrotoxicosis.
12. โข Thyroiditis
โข Acute tenderness in a diffuse swelling,
sometimes with severe pain, is suggestive of
an acute viral thyroiditis (de Quervainโs). It
may produce transient clinical
hyperthyroidism with an increase in serum T4
13. Nodular goitres
โข Multinodular goitre
โข Most common is the multinodular goitre,
especially in older patients. The patient is usually
euthyroid but may be hyperthyroid or borderline
with suppressed TSH levels but normal T4 and T3.
Multinodular goitre is the most common cause of
tracheal and/or oesophageal compression and
can cause laryngeal nerve palsy. It may also
extend retrosternally.
14. โข Solitary nodular goitre
โข Such a goitre presents a difficult problem of diagnosis.
โข Malignancy should be considered in any solitary nodule
โ however, the majority of such nodules are cystic or
benign.
โข A history of rapid enlargement, associated lymph
nodes or occasionally pain in such a situation suggests
the possibility of thyroid carcinoma.
โข Risk factors for malignancy include previous irradiation,
long-standing iodine deficiency and occasional familial
cases.
โข Solitary toxic nodules are quite uncommon and may be
associated with T3 toxicosis.
15. โข Fibrotic goitre
โข Fibrotic goitre (Riedelโs thyroiditis) is a rare
condition, usually producing a โwoodyโ gland.
It is associated with other midline fibrosis and
is often difficult to distinguish from carcinoma,
being irregular and hard.
16. โข Malignancy
โข In addition to thyroid carcinomas, the thyroid
is rarely the site of a metastatic deposit or the
site of origin of a lymphoma.
17. Investigations
Thyroid function tests โ TSH plus free T4 or T3
Thyroid antibodies โ to exclude autoimmune aetiology.
Ultrasound. Ultrasound with high resolution is a sensitive
method for delineating nodules and can demonstrate
whether they are cystic or solid.
18. Chest and thoracic inlet X-rays to detect tracheal
compression and large retrosternal extensions in
patients with very large goitre or clinical symptoms.
Fine-needle aspiration (FNA). In patients with a solitary
nodule or a dominant nodule in a multinodular goitre,
there is a 5% chance of malignancy; in view of this, FNA
should be performed.
19. Thyroid scan (125I or 131I) can be useful to
distinguish between functioning (hot) or non-functioning
(cold) nodules.
A hot nodule is only rarely malignant; however,
a cold nodule is malignant in only 10% of cases
and FNA has largely replaced isotope scans in
the diagnosis of thyroid nodules.
20. Treatment
โข Euthyroid goitre
โข Many goitres are small, cause no symptoms
and can be observed (including self-monitoring
by the patient in the long term). In
particular, during puberty and pregnancy a
goitre associated with euthyroidism rarely
requires intervention and the patient can be
reassured that spontaneous resolution is
likely.
21. Indications for surgical intervention are:
The possibility of malignancy. A history of rapid growth, pain,
cervical lymphadenopathy, change in voice or previous irradiation to
the neck are worrying features. A positive or suspicious FNA makes
surgery mandatory.
Pressure symptoms on the trachea or, more rarely, oesophagus. The
possibility of retrosternal extension should be excluded.
Cosmetic reasons. A large goitre is often a considerable anxiety to
the patient even though functionally and anatomically benign.
22. โข Toxic nodule
โข This is initially with antithyroid drugs but
surgery or radioiodine is often required.
