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430 Chapter 11: Endocrine system

patients are euthyroid with a goitre, occasionally one or Aetiology/pathophysiology
more nodules develop, which are TSH-independent and Solitary thyroid nodules are most commonly benign
so cause thyrotoxicosis. (over 90%). Causes include the following:
Benign follicular adenoma: Single lesions with well-

Macroscopy/microscopy developed fibrous capsules. Adenomas are not under
The thyroid is enlarged with irregular nodules of vary- the control of TSH and continue to secrete thyroid
ing sizes. Nodules may be cystic, haemorrhagic and fi- hormones, which may result in hyperthyroidism.
brosed.Microscopyrevealshyperplasticacini,withvary- There are low levels of circulating TSH and hence sup-
ing amounts of colloid. pression of the remainder of the thyroid gland.
Colloid nodule that may be a dominant nodule in a

multinodular goitre (see page 428).
Complications
Malignant tumours of the thyroid follicle cells.
Enlargement of the gland can cause tracheal compres-
Thyroid cyst (15–25%): These may be simple cysts
sion leading to shortness of breath and choking. This is
or bleeding into a colloid nodule or adenoma. About
more common with retrosternal goitre, when the nod-
15% are necrotic papillary tumours.
ule(s) are in the isthmus. Toxic multinodular goitre has
a particularly high incidence of cardiac arrhythmias and
Clinical features
other cardiac complications.
Patients may present with a palpable lump or may be
diagnosed on incidental imaging. Features suggestive of
Investigations
malignancy:
Thyroid function tests (TSH and thyroid hormone lev-
Rapid painless growth.
els) are used to assess thyroid status. A chest X-ray can
Family history of thyroid tumours or MEN 2 syn-
demonstrate any retrosternal mass or tracheal devia-
drome (see page 450).
tion. Ultrasound scanning of the thyroid may be useful
History of neck irradiation exposure.
to examine the structure of the thyroid and nature of
Hoarseness and vocal cord paralysis suggesting recur-
lesions. Isotope scans are used to demonstrate areas of
rent laryngeal nerve palsy.
increaseduptakeintoxicmultinodulargoitres.Cystsand
Malignancy is more common in children and patients
nodules may be aspirated by fine needle aspiration for
over 60 years.
cytology.
Investigations
Management Thyroid function tests are used to determine thyroid
Subtotal thyroidectomy may be required for cosmetic
status. Isotope scans may also be used to demon-
reasons or due to compression symptoms or thyrotoxi-
strate either a cold nodule, a hyperactive gland (toxic
cosis. Patients must be medically treated and euthyroid
multinodular goitre) or a ‘cold’ gland containing a
before surgery.
‘hot’ nodule (toxic adenoma). Cold nodules suggest
malignancy.
Solitary thyroid nodule Ultrasound scan may be used to determine the
anatomyofthelesionanddistinguishsolidfromcystic
Definition nodules.
A solitary mass within the thyroid gland that may be Fine needle aspiration for cytology is used to differen-
solid or cystic. tiate benign cells, suspicious cells or malignant cells.
Incidence Management
5% of population have a palpable solitary thyroid nod- Benign lesions only require treatment if they cause hy-
ule. Up to 50% of population have a solitary nodule at perthyroidism or for cosmetic reasons. Treatment op-
postmortem. tions include surgical excision and radioactive iodine.