Pediatric Examination and Board Review (64 page)

8.
(C)
Polyphagia, which is a symptom of hyperthyroidism. The most common manifestation of hypothyroidism in children is subnormal growth velocity leading to short stature. The growth retardation can be present for many years before other symptoms occur. Other manifestations of hypothyroidism specific to children include delayed bone maturation and sexual disorders, including both delayed and precocious puberty. Other symptoms of hypothyroidism include bradycardia, cold intolerance, fatigue, constipation, muscle aches, and dry skin.

9.
(E)
All of the above.

10.
(D)
Subacute thyroiditis. Patients with subacute thyroiditis may present initially with hyperthyroidism, which is followed by transient hypothyroidism associated with recovery. Thyroid function then typically returns to normal with resolution of the inflammation.

11.
(A)
Peripheral conversion from thyroxine (T4). Approximately 70-90% of circulating T3 is derived from monodeiodination of T4 in peripheral tissues, with the remainder derived from the thyroid gland. Thus the activity of the deiodination enzymes is critical to the production of intracellular T3 and critical for the maintenance of normal cellular activity. In contrast, most T4 is made in the thyroid gland.

12.
(D)
T3, which is the active form of thyroid hormone. T4 is the major thyroid hormone in the blood and metabolized to T3 and reverse T3, which is not biologically active. TSH is secreted from the pituitary gland under the control of TRH from the hypothalamus and controls thyroid hormone production and release from the thyroid gland.

13.
(D)
Programs that use TSH can miss central hypothyroidism. Most children with central hypothyroidism have normal to low normal serum TSH concentrations, and thus they will be missed if only TSH is measured. Neonates with congenital hypothyroidism typically have no specific signs at birth. The possibility of central hypothyroidism needs to be considered in any infant with other signs of pituitary deficiency, such as hypoglycemia, prolonged neonatal jaundice, micropenis, midline facial defects, or poor growth.

14.
(E)
Thyroid dysgenesis. Congenital hypothyroidism occurs in approximately 1 in 4000 newborns and is the most preventable cause of mental retardation, if detected and treated early. Neonates with congenital hypothyroidism usually have very few signs and symptoms, thus underlining the importance of the neonatal screen for diagnosis. Thyroid dysgenesis (agenesis, hypoplasia, or ectopic thyroid) is the leading cause of congenital hypothyroidism in iodine-sufficient areas, followed by, in order of decreasing incidence: transient hypothyroidism, thyroid dyshormonogenesis, and TSH deficiency.

15.
(B)
Retarded central nervous system development. Thyroid hormones exert effects that are most obvious during infancy and early childhood. Brain development depends on thyroid function in the first 3 years of life. The early detection of congenital hypothyroidism and early treatment prevents the development of mental retardation that would occur in untreated cases. The initial goal of treatment of congenital hypothyroidism is to restore the T4 concentration to the upper half of the normal range as rapidly as possible.

16.
(C)
Graves disease. Virtually all children with Graves disease have a goiter, and 50-75% have mild ophthalmopathy. Severe ophthalmopathy is much less common in children than in adults. Eye findings may include lid lag, infrequent blinking, appearance of a stare because of retraction of the upper lid, exophthalmos, and ophthalmoplegia. Graves disease occurs most commonly in the 11- to 15-year age group, and girls are affected more frequently than boys.

17.
(A)
Delayed deep tendon reflexes. The development of hyperthyroidism in children can be insidious. Typical symptoms include nervousness and jitteriness, sleep disorders leading to fatigue, heat intolerance, tachycardia and palpitations, and a decline in school performance. Children with Graves disease tend to have greater emotional lability and behavioral disturbances than adults. In prolonged hyperthyroidism in children, accelerated linear growth and advanced bone maturation can be seen. Delayed deep tendon reflexes are seen in hypothyroidism.

18.
(A)
Antithyroid drugs can cause granulocytopenia. Blocking thyroid hormone synthesis with methimazole is typically the initial therapy of hyperthyroidism in a young child. Most children need to be on antithyroid drugs for many years, and close supervision is necessary to monitor thyroid function tests. Side effects of these drugs include rash, granulocytopenia, and liver failure. Ablation of the thyroid gland with radioactive iodine is another treatment option for Graves disease but usually not the preferred initial treatment in children. This treatment option is used extensively in adults. Subtotal surgical thyroidectomy is another treatment option but is usually reserved for children who fail medical therapy or experience serious side effects of antithyroid medications. The availability of an experienced thyroid surgeon is an important criterion for the success of this treatment option. Serious complications of subtotal thyroidectomy include hypoparathyroidism and recurrent laryngeal nerve damage. Corticosteroids can be used in thyroid storm to prevent the peripheral conversion of T4 to T3.

19.
(B)
The onset of signs and symptoms can be delayed for 8-9 days. Neonatal Graves disease occurs in approximately 2% of neonates born to mothers with Graves hyperthyroidism. It can be severe, and even life threatening, if not treated properly. It occurs following the transplacental passage of TSH receptor–stimulating antibody. The time of onset and severity of symptoms is variable and depends on the transplacental passage of blocking antibodies and antithyroid drugs. The characteristic manifestations of neonatal Graves disease include irritability, tachycardia, poor weight gain, diarrhea, thyromegaly, and exophthalmus. The treatment consists of iodine or antithyroid drugs, corticosteroids, and propranolol. Neonatal Graves typically resolves spontaneously in 3-12 weeks.

20.
(E)
Euthyroid sick syndrome, which is an alteration of thyroid hormone levels seen in severe illness. Patients have a decrease in T3 because of an increased metabolism of TT4 to the bioinactive reverse T3, which is characteristically elevated. The lowest levels of T3 and T4 have been associated with increased mortality. It is controversial whether euthyroid sick syndrome is an adaptive phenomenon to decrease metabolic rate, an important contributor of the disease process, or just an associated marker of disease severity. It is controversial whether treatment with thyroid hormone is beneficial or harmful.

S
UGGESTED
R
EADING

Counts D, Varma SK. Hypothyroidism in children.
Pediatr Rev.
2009;30:251-258.

Fisher DA, Grueters A. Disorders of the thyroid in the newborn and infant. In: Sperling MA, ed.
Pediatric Endocrinology.
3rd ed. Philadelphia, PA: WB Saunders; 2008:198-226.

Fisher DA, Grueters A. Thyroid disorders in childhood and adolescence. In: Sperling MA, ed.
Pediatric Endocrinology.
3rd ed. Philadelphia, PA: WB Saunders; 2008:227-253.

Huang SA, Larsen PR. Autoimmune thyroid disease. In: Radovick S, MacGillivray MH, eds.
Pediatric Endocrinology
,
A Practical Clinical Guide
. Totowa, NJ: Humana Press; 2003:291-307.

Larsen CA. Congenital hypothyroidism. In: Radovick S, MacGillivray MH, eds.
Pediatric Endocrinology
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A Practical Clinical Guide
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CASE 41: A 14-MONTH-OLD WITH A SEIZURE

A 14-month-old child presents to the emergency department following a brief tonic-clonic seizure. The child has no previous history of seizures. He has not been ill recently and has had a normal appetite. He was exclusively breastfed until 6 months of age when his mother added in cereal (mixed with breast milk) and some jar baby foods. He continues to breast-feed. It is early spring, and it has been a particularly dark and dreary winter. His mother has concerns that the child is not yet walking. He is afebrile on physical examination and is normal size for both height and weight.

SELECT THE ONE BEST ANSWER

1.
On physical examination, the patient has a positive Chvostek sign. This is typical in which of the following circumstances?

(A) hypophosphatasia

(B) hypoglycemia

(C) hypocalcemia

(D) hypophosphatemia

(E) hypomagnesemia

2.
Which of the following are clinical features of hypocalcemia?

(A) laryngospasm, shortened QT interval on electrocardiogram (ECG), and a positive Trousseau sign

(B) laryngospasm, prolonged QT interval on ECG, and a positive Trousseau sign

(C) paresthesias, prolonged QT interval on ECG, and a negative Trousseau sign

(D) paresthesias, shortened QT interval on ECG, and a positive Trousseau sign

(E) paresthesias, normal QT interval on ECG, and a positive Trousseau sign

3.
The patient’s total calcium is low at 6 mg/dL, with a low ionized calcium of 3 mg/dL. What is the most likely diagnosis if the serum phosphate is 2.5 mg/dL?

(A) nutritional rickets

(B) hypoparathyroidism

(C) X-linked hypophosphatemic rickets

(D) pseudohypoparathyroidism (PHP)

(E) pseudopseudohypoparathyroidism (PPHP)

4.
What is the most likely diagnosis if the total calcium is 6 mg/dL, ionized calcium of 3 mg/dL, and serum phosphate 8 mg/dL?

(A) nutritional rickets

(B) hypoparathyroidism

(C) X-linked hypophosphatemic rickets

(D) PPHP

(E) low serum albumin

5.
What is the most likely diagnosis if the total calcium is 6 mg/dL, ionized calcium of 3 mg/dL, serum phosphate 8 mg/dL, and PTH 130 pg/mL (normal: 9-52)?