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CHAPTER 40

Thyroid and Parathyroid Glands

Abdulrasheed A. Nasir
Emmanuel A. Ameh
Ashley Ridout

Demographics Test of Hypothalamic Pituitary Axis
Diseases of the thyroid gland were demonstrated to occur in 3.7% of The test for thyrotropin-releasing hormones (TRH) is given intravenous-
4,819 school-aged children at initial examination in the United States; ly. The basal level of serum TSH is raised in a normal individual at 20
in a followup examination 20 years later, the prevalence had increased minutes and returned to normal in 120 minutes. In hypothyroidism, the
to 10.5%. About half of these are diffuse gland hypertrophy or simple already elevated TSH shows a much higher rise, but there is no response
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goiter. Thyroiditis was the second most common abnormality, followed in hyperthyroidism. This is known as the TRH stimulation test.
by thyroid nodules and functional disorders. Malignant neoplasms are Imaging
exceedingly rare, with only two papillary thyroid carcinomas found in a Several imaging modalities are available to assist in evaluating the thy-
population of nearly 5,000 children followed up for three years. Data on roid gland, among them ultrasonography (US), computed tomography
thyroid diseases in African children are scanty. One series reported four (CT), magnetic resonance imaging (MRI), and scintigraphy.
cases of thyroid tumours in children over a ten-year period in Enugu, Ultrasonography
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Nigeria. Three of these were adenomas and the remaining one was
a papillary carcinoma. All of the patients were girls younger than 10 Ultrasound imaging is very useful in the evaluation of thyroid disease
years of age. Data from the United States, based on the National Cancer and can determine whether a neck mass actually arises from the thyroid
Registry, reported the annual incidence of thyroid tumours as 0.54 per and whether multiple nodules are present. It allows differentiation of
100,000 individuals. 3 solid and cystic lesions. It is useful in detection of thyroid nodules and
measurement of their volume. Goiter volume can be assessed precisely
Evaluation of Thyroid Diseases with US and is a useful guide in the assessment of goiter shrinkage
Assessment of Thyroid Function response under medical treatment. Although this modality can be used
It is often necessary to determine whether a patient has a hyperactive, in a clinical setting, it may not be appropriate for mass surveys.
normal, or hypoactive thyroid function. A detailed history and careful Computed tomography and magnetic resonance imaging
clinical examination will reveal the diagnosis. A CT scan is useful in the study of the architecture of the thyroid gland
Measurement of Thyroid Hormones in the Serum and its relation to the surrounding organs. It can be useful in assessing
Thyroid functional status can be established by estimating the serum retrosternal extension of the thyroid. Pituitary or hypothalamic tumours
thyroid hormones and thyroid-stimulating hormone (TSH, or thyrotro- can be seen, as can metastatic lesions of thyroid carcinoma, which are
pin), which are the most important diagnostic tests. Levels of free T usually solitary. MRI provides a good soft tissue resolution and helps in
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and free T in serum provide a better assessment of the thyroid status further ascertaining the architecture of the thyroid gland.
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than total T and T . The levels of T and T are decreased in hypothy- Scintigraphy
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roidism, and they are increased in hyperthyroidism. Free T and TSH Scintigraphy tests are based on the avidity or otherwise of the thyroid
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are the most common useful tests in paediatric thyroid disorders, but to absorb or release the isotope of iodine or technetium and the dis-
test results must be interpreted in conjunction with the child’s overall tribution of the isotope within the gland. Isotopic scanning provides
clinical condition. T levels usually need to be measured only when a information on the size, shape, position, function, and possible nature
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patient is suspected of having hyperthyroidism but has normal T lev- of thyroid swelling. The uptake by the thyroid of a low dose of either
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els, particularly in cases of toxic nodule, multinodular goiter, or recur- radioiodine I or I and technetium-99m pertechnetate will demon-
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rent Graves’ disease. Graves’ disease is discussed later in this chapter. strate the distribution of activity in the whole thyroid gland. The test is
Thyrotropin is nearly always decreased in the hyperthyroid state and of value in a toxic patient with a nodule or nodularity of the thyroid.
elevated in hypothyroidism and is an extremely sensitive measure of Localisation of overactivity in the gland will differentiate between a
hypothyroid state. The plasma free T level is a measure of biologically toxic nodule with suppression of the remainder of the gland and toxic
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active thyroid hormone, unaffected by protein binding. When total multinodularity goiter with several areas of increased uptake with
plasma T and T are measured, it is necessary to consider the level of important implications for therapy. Scintigraphy may also be useful in
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unbound biologically active hormone. detecting ectopic thyroid tissue or metastatic thyroid carcinoma.
Serum Thyroid Antibodies Fine Needle Aspiration Biopsy and Cytology
The autoantibody status is important in determining thyroid autoim- Thyroid tissue is obtained percutaneously with a 22–25-gauge needle
mune diseases. Serum thyroid antibodies are frequently elevated in attached to a 20-ml syringe fixed in a syringe holder. Fine needle aspira-
autoimmune thyroid disorders. Approximately 80% of patients with tion (FNA) is useful in diagnosing papillary, medullary, and anaplastic
Hashimoto’s disease have elevated antimicrosomal autoantibodies, carcinomas. There is small risk of false negative results. It is difficult
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and most patients with Graves’ disease have detectable thyroid-stimu- to differentiate between simple and malignant follicular tumours by
lating immunoglobulins. The presence of these antibodies is helpful in FNA cytology.
the diagnosis of autoimmune thyroid disorders.