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Thyroid and Parathyroid Glands 265

be considered in any child with an unexplained growth spurt, sympathy Hypothyroidism
(e.g., muscle weakness, paraesthesia) or behavioural problems. The Hypothyroidism is a clinical state in which there is reduced thyroid
gland is uniformly enlarged, smooth, firm, and nontender. It may be so hormonal activity. This is rarely due to thyroid hypofunction sec-
vascular that a bruit is audible over it. ondary to reduced TSH stimulation resulting from hypopituitarism.
Laboratory evaluation generally reveals elevated free T and Hypothyroidism may result from a defect anywhere in the hypothalam-
4
decreased TSH levels. In 10–20% of patients, only the T level is ic-pituitary-thyroid axis (Table 40.1).
3
elevated, a condition referred to as T toxicosis. The diagnosis of Graves’
3 Table 40.1: Causes of hypothyroidism.
disease is established by the presence of TSH-receptor antibodies.
Type of
Management hypothyroidism Cause
The treatment of Graves’ disease is palliative, with the goal to allow
Following subtotal thyroidectomy
natural resolution of the underlying autoimmune process. The natural
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course of untreated Graves’ disease is unpredictable. The treatment is Hypophysectomy
Iatrogenic
designed to reduce the production and secretion of the thyroid hormone. Radio-iodine treatment for thyroitoxicosis
This could be specific or nonspecific. Specific measures include the use
Excessive ingestion of para-aminosalicylic (PAS) acids,
of antithyroid drugs (carbimazole, neomercazole, potassium perchlo- phenylbutazone, or antithyroid drugs
rate). Nonspecific measures include rest and sedation.
Iodine deficiency Area of endemic goiters
Initial therapy is with methimazole or propylthiouracil, which reduces
thyroid hormone production by inhibiting follicle cell organification of Autoimmune Secondary to thyroid antibodies
iodide and the coupling of iodotyrosines. Propylthiouracil also inhibits thyroiditis
peripheral conversion of T to T , and may be the drug of choice if rapid Deficiency or absence of enzymes needed for thyroid
4 3 Dyshormonogenesis
alleviation of thyrotoxicosis is desired. Both agents may possess some hormone synthesis
immunosuppressive activity. Methimazole is preferred in most cases
Absence of thyroid gland (very rare) or ectopic thyroid
due to its increased potency, longer half-life, and associated improved gland
compliance. The initial dose in adolescents is 30 mg once daily, Congenital Antenatal goitrogens
adjusted for younger patients. The dosage is reduced to 10 mg when the
Pituitary-hypothalamic disease
patient becomes euthyroid with normal T and T .
3 4
The thyroid gland decreases in size in about half of the patients.
Thyroid enlargement with therapy signals either an intensification of Congenital hypothyroidism
the disease or hypothyroidism with overtreatment. 18
Ninety percent of paediatric hypothyroidism is congenital, detected by
In general, the disease remission rate is approximately 25% after 2
22
years of treatment, with a further 25% remission every 2 years. The neonatal screening programmes, and results from dysgenesis of the thy-
roid gland. Screening programmes have dramatically altered detection
resolution rate is decreased if TSH-receptor antibodies persist during
and management of congenital hypothyroidism. In the United Kingdom,
and after treatment.
all newborns are screened for congenital hypothyroidism as part of a
Surgery national screening programme, which also includes tests to exclude phe-
Surgery is usually contraindicated in children due to the high postopera- nylketonuria and cystic fibrosis. The worldwide incidence of congenital
tive incidence of hypothyroidism (35%), recurrence, tetany (17%), and hypothyroidism is reported as 1 in 4,000 infants. However, the true inci-
of permanent hypoparathyroidism (10%). 12 dence is lower in African Americans and higher in Hispanic and Native
Indications for surgery in children with Grave’s disease include: American populations. Two-thirds of these babies have a rudimentary
19
• idiosyncratic reaction to antithyroid drugs; gland, and complete absence of thyroid tissue is noted in the rest of the
patients. The rudimentary gland may be ectopic. 18
• progressive enlargement of the gland, even in a euthyroid state;
The severe form of hypothyroidism in children is cretinism, which is
• contraindication to radioactive iodine; also congenital, and the child may be born with or without a goiter. The
child is usually underdeveloped both physically and mentally. There
• recurrent hyperthyroidism;
may be associated deafness, mutism, and neuromotor disorders (e.g.,
• patients who refuse radioiodine; spastic paraplegia, dysarthria). 12
• failed medical therapy; and Evaluation
Infants with congenital hypothyroidism are often normal size at birth,
• large thyroid gland compressing the airway.
which is a reflection of the fact that thyroid hormones do not appear
Surgery in the form of either subtotal thyroidectomy or total to be necessary for foetal growth. Physical features are not apparent in
thyroidectomy in the suitably prepared patient may be performed. the first week of life. Prolonged neonatal jaundice is usually the first
Preoperative antithyroid medication should be administered to decrease symptom, followed by feeding problems, lethargy, constipation, and
T and T levels to the normal range. Beta-blocking agents such as poor tone. Examination often reveals coarse facies; a large protruding
3 4
propranolol may be used to ameliorate the adrenergic symptoms of tongue; large open fontanelles; a hoarse cry; coarse, dry, and mottled
hyperthyroidism. skin; umbilical hernia; and delayed growth. In severe cases, these fea-
In addition, Lugol’s iodine solution, 5 to 10 drops per day, should tures appear within 4 to 8 weeks of birth. 24
be administered for 4 to 7 days before thyroidectomy to reduce the Serum T , T , and resin uptake are decreased, whereas TSH is
3
4
vascularity of the gland. elevated. Assessment of skeletal age (by x-ray of the knee) may show
The incidence of hypothyroidism after subtotal thyroidectomy is bone maturation of less than 36 weeks gestation, suggesting intrauterine
12–54%, and the hypothyroidism may be subclinical in up to 45% hypothyroidism.
of children. The rate of recurrent hyperthyroidism is approximately Treatment
23
13%. The relapse rate may increase with time after surgery. Near total Treatment is by lifetime thyroid hormone replacement. Synthetic
thyroidectomy is advocated by some authors. 2 (laevo-) thyroxin is used at a dosage of 10 mg/kg per day, starting with
25 mg per day and increasing to 100 mg per day.