Pediatric Examination and Board Review (63 page)

FIGURE 40-1.
A child with a prominent goiter.

SELECT THE ONE BEST ANSWER

1.
What other information would be most helpful to narrow your differential diagnosis?

(A) birth history

(B) newborn screen

(C) developmental history

(D) growth pattern

(E) pubertal history

2.
Which of the following tests would you order first?

(A) total thyroxine (TT4), free thyroxine index (FTI), thyrotropin (TSH), and thyroid antibodies

(B) total triiodothyronine (T3), reverse T3, TSH

(C) TT4, reverse T3, TSH, thyroid antibodies

(D) thyroid ultrasound

(E) thyroid scan

3.
The thyroid gland is tender to palpation, and the child reports that he/she has had an upper respiratory tract infection the last few days. What would be at the top of your differential diagnosis?

(A) Hashimoto thyroiditis

(B) hyperthyroidism

(C) Graves disease

(D) subacute thyroiditis

(E) euthyroid sick syndrome

4.
What would the most likely diagnosis be if the TT4 was 4.5 μg/dL (normal: 5-11.5) and FTI 3 (normal: 6.0-10.5)?

(A) Hashimoto thyroiditis

(B) Graves disease

(C) low thyroxin-binding globulin (TBG)

(D) subacute thyroiditis

(E) euthyroid sick syndrome

5.
What would you expect the TSH to be for the child described in question 4? (normal: TSH 0.4-6.4 mU/L)

(A) less than 0.01 mU/L

(B) 0.01 mU/L

(C) 1.0 mU/L

(D) 6.0 mU/L

(E) 15 mU/L

6.
What would the most likely diagnosis be if the TT4 was 3 μg/dL, FTI 7, and the child did not have a goiter?

(A) Hashimoto thyroiditis

(B) Graves disease

(C) low TBG

(D) subacute thyroiditis

(E) euthyroid sick syndrome

7.
What would be the most likely diagnosis if the TT4 was 10 μg/dL, FTI 10, TT3 180 ng/dL (normal: 80-195), and thyroid antibodies were positive?

(A) Hashimoto thyroiditis

(B) Graves disease

(C) high TBG

(D) subacute thyroiditis

(E) none of the above

8.
Which of the following is not a symptom or sign of hypothyroidism in children?

(A) growth retardation

(B) bradycardia

(C) polyphagia

(D) pubertal disorder

(E) delayed bone maturation

9.
Which of the following depends on thyroid hormone?

(A) somatic growth

(B) bone growth

(C) tooth eruption

(D) A and B

(E) all of the above

10.
Which of the following is not a cause of acquired hypothyroidism?

(A) autoimmune thyroiditis

(B) late-onset thyroid dysgenesis

(C) TSH deficiency

(D) subacute thyroiditis

(E) C and D

11.
Most circulating triiodothyronine is derived from

(A) peripheral conversion from thyroxine

(B) thyroid gland

(C) pituitary gland

(D) parathyroid glands

(E) hypothalamus

12.
Which of the following is the biologically active form of thyroid hormone?

(A) TRH (thyrotropin-releasing hormone)

(B) TSH

(C) T4

(D) T3

(E) Reverse T3

13.
Which of the following is true regarding newborn screening for congenital hypothyroidism?

(A) Programs that use TT4 can miss central hypothyroidism.

(B) The optimum time to collect the sample is within the initial 24 hours of life.

(C) Transient hypothyroidism can be missed.

(D) Programs that use TSH can miss central hypothyroidism.

(E) Programs that use TT3 can miss central hypothyroidism

14.
Which of the following is the leading cause of congenital hypothyroidism in iodine-sufficient areas?

(A) TRH deficiency

(B) TSH deficiency

(C) thyroid dyshormonogenesis

(D) transient hypothyroidism

(E) thyroid dysgenesis

15.
What is the most worrisome consequence of untreated congenital hypothyroidism?

(A) prolonged physiologic jaundice

(B) retarded central nervous system development

(C) delayed bone maturation

(D) soft tissue myxedema

(E) poor growth

16.
You notice that the patient has exophthalmos. What diagnosis would be most likely?

(A) Hashimoto thyroiditis

(B) Hashitoxicosis

(C) Graves disease

(D) iodine deficiency

(E) TSH-secreting pituitary tumor

17.
All of the following are signs or symptoms of hyperthyroidism except

(A) delayed deep tendon reflexes

(B) nervousness

(C) fatigue

(D) palpitations

(E) A and C

18.
Which of the following statements is true regarding the treatment of Graves disease?

(A) antithyroid drugs can cause granulocytopenia

(B) radioactive iodine should only be used in thyroid storm

(C) subtotal surgical thyroidectomy is the preferred initial treatment in children

(D) corticosteroids inhibit release of T4 from the thyroid gland

(E) thyroid storm is a common complication

19.
Which of the following is true regarding neonatal Graves disease?

(A) neonatal Graves occurs in 20% of neonates born to mothers with Graves

(B) the onset of signs and symptoms can be delayed for 8-9 days

(C) no treatment is necessary because it tends to be self-limited

(D) neonates are typically asymptomatic

(E) the disease is caused by transplacental passage of thyroid hormone

20.
What would the most likely diagnosis be if this child was in the intensive care unit following cardiac surgery and had a TT4 of 4 μg/dL, FTI 4, TT3 of 50 ng/dL, reverse T3 450 ng/dL, and TSH 4 mU/L (normal: 0.4-6.4)?

(A) TRH deficiency

(B) TSH deficiency

(C) TBG deficiency

(D) Hashimoto thyroiditis

(E) euthyroid sick syndrome

ANSWERS

1.
(D)
Growth pattern. Children with hypothyroidism often manifest slowing of their growth, whereas children with hyperthyroidism eventually have accelerated growth if the disorder is not detected and treated appropriately.

2.
(A)
TT4, FTI, TSH, and thyroid antibodies. Serum TT4 is the major thyroid hormone in the blood, and laboratory tests measure both bound and unbound T4. Because most T4 is bound to thyroxin-binding globulin (TBG), transthyretin, or albumin, levels of binding proteins affect the TT4 concentration. Thus the levels of free and total thyroid hormone may not be concordant. Free thyroxin index is a calculation that reflects bioavailable thyroid hormone because it takes into account the amount of binding protein. TSH is secreted from the pituitary under the control of thyrotropin-releasing hormone (TRH) from the hypothalamus, and through negative feedback from thyroid hormones. Several antibodies against thyroid antigens have been demonstrated in chronic autoimmune thyroiditis, and these levels should be determined in a child with a goiter. TT3 is the active form of thyroid hormone, but it is usually not measured with the initial screen. Reverse T3 is an inactive metabolite of TT4, and measurement is important in the diagnosis of euthyroid sick syndrome. Thyroid ultrasound or thyroid scan would be indicated if nodules were detected.

3.
(D)
Subacute thyroiditis. Subacute thyroiditis is a self-limited inflammation of the thyroid gland that usually follows an upper respiratory tract infection. The thyroid gland can be very tender to palpation. There is often a pattern of hyperthyroidism secondary to inappropriate release of thyroid hormone. Signs and symptoms of hyperthyroidism can persist for 1-4 weeks, after which transient hypothyroidism typically develops with recovery of the gland. The total course of illness can last 2-9 months. Treatment is typically with anti-inflammatory drugs. Children with euthyroid sick syndrome do not present with a goiter, and the presentation usually does not follow a mild illness.

4.
(A)
Hashimoto thyroiditis. The most common abnormality of thyroid function in children is hypothyroidism, usually caused by autoimmune (Hashimoto) thyroiditis. Hashimoto thyroiditis is characterized by circulating thyroid antibodies and varying degrees of thyroid dysfunction. It can present with or without a goiter. It is more prevalent in girls, and many patients have a family history of autoimmune thyroid disease. Spontaneous remission has been reported. Other causes of acquired hypothyroidism include late-onset thyroid dysgenesis or dyshormonogenesis, TSH deficiency, thyroid damage, and iodine deficiency. T4 replacement is the treatment of choice for hypothyroidism.

5.
(E)
The answer is 15 mU/L. In hypothyroidism secondary to Hashimoto thyroiditis, the TSH will be elevated.

6.
(C)
Low TBG. TT4 measures both bound and free T4. In cases where the TBG is low, measured T4 levels will be low, even though free thyroid hormone levels are normal. High-dose glucocorticoids can lower TBG levels, and low TBG levels can also run in families. In contrast, pregnancy or estrogen administration is a common cause of high TBG levels.

7.
(A)
Hashimoto thyroiditis. There is a spectrum of presentation for Hashimoto thyroiditis. Patients can present with a picture of hyperthyroidism (hashitoxicosis), euthyroidism, or hypothyroidism. Patients typically have a nontender goiter and evidence of thyroid antibodies.