الاثنين، 24 ديسمبر 2012

MCQs In Pediatric Endocrinology


Q 1

A 14-year-old girl has a 3-month history of a progressively enlarging mass in the left thyroid lobe. She has developed hoarseness over the past 2 weeks. Physical examination reveals a 3 cm firm mass in the left upper lobe of the thyroid gland. There is no associated adenopathy.
Of the following, the MOST helpful test for establishing the diagnosis is:

A.  fine-needle aspiration biopsy of the thyroid gland
B.  measurement of the thyroid-stimulating hormone level
C.  measurement of the thyroxin level
D.  radionuclide scan of the thyroid gland
E.   ultrasonography of the thyroid gland

Answer

A



            Most thyroid nodules present as painless masses near the midline of the lower neck. The time of onset; rate of growth; and presence of pain, hoarseness, and dysphagia as well as systemic symptoms of hypo- and hyperthyroidism are important to identify. Prior radiation exposure significantly increases the likelihood of malignancy. There may be an increased risk of malignancy in certain illnesses, such as iodine deficiency, Hashimoto thyroiditis, and Grave disease. Familial syndromes such as Pendred or Gardner syndromes as well as multiple endocrine neoplasia (MEN) 2A and 2B clearly increase the risk of thyroid carcinoma. Prophylactic thyroidectomy is recommended for children who have high-risk syndromes.

            Physical examination should include assessment for vocal cord mobility and cervical lymphadenopathy as well as for size and characteristics of the thyroid nodule.

            Although measurements of thyroid functions, including thyroid-stimulating hormone levels and thyroxin levels, should be obtained, these are rarely abnormal in asymptomatic individuals and do not differentiate benign from malignant lesions. Chest radiography and lateral neck films usually appear normal, but may show radiopaque psammoma bodies in papillary carcinomas. Thyroid gland scintigraphy (thyroid scan) usually is performed with technetium 99 or iodine 123. The degree of isotope concentration differentiates a cold nodule from a hot nodule. 

            Ultrasonography can be useful for differentiating a solid from a cystic mass and for evaluating for multiple nodules such as a multinodular goiter. Cystic lesions, however, may be malignant.

            Fine-needle aspiration (FNA) biopsy is considered by most authors to be the diagnostic procedure of choice for assessing solitary thyroid nodules. Based on results of FNA, an experienced cytopathologist can segregate nodules accurately into negative, nondiagnostic, or probable malignant categories. The overall diagnostic accuracy of FNA cytology is approximately 90%. Because of this high diagnostic accuracy, thyroid scans and ultrasonography are usually not necessary.

            Total thyroidectomy is not recommended unless high-risk malignancy is diagnosed definitively. Hemithyroidectomy occasionally is recommended for biopsy if FNA cytology results are equivocal and usually is recommended for definitive diagnosis of positive FNA cytology.

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Q2 


A 16-year-old otherwise healthy girl presents for evaluation of primary amenorrhea. Physical examination reveals a height of 55.5 in (140 cm), weight of 110 lb (50 kg), no breast tissue, and Sexual Maturity Rating (Tanner) stage 3 pubic hair development. Her mother's height is 68 in (173 cm), and her father's height is 70 in (178 cm).

Of the following, the MOST likely diagnosis is:



A.  androgen insensitivity (testicular feminization) syndrome

B.  constitutional delay of growth and development

C.  familial short stature

D.  imperforate hymen

E.  Turner syndrome

Answer

E



The girl in the vignette has primary amenorrhea, defined as the absence of menses by age 14 years in a patient who has no secondary sexual characteristics (eg, breast development) or by 16 years when such characteristics are present. She has short stature, normal weight, absent breast tissue (suggesting an absence of ovarian estrogen), and normal pubic hair (confirming the presence of adrenal androgens). These clinical findings are characteristic of gonadal dysgenesis caused by Turner syndrome. Gonadal dysgenesis is the most common cause of primary amenorrhea, and Turner syndrome is the most common cause of gonadal dysgenesis.


Individuals who have androgen insensitivity (testicular feminization) syndrome are chromosomally male (XY genotype) and have male gonads that produce normal amounts of testosterone. However, because the androgen receptors do not function normally, male external genitalia do not develop and, in contrast to the patient in the vignette, pubic and axillary hair are sparse. Affected individuals have normal stature and breast development.

            The most common cause of pubertal delay is constitutional delay of growth and development, which often is familial and occurs more commonly in boys. Height, pubertal development, and bone age are delayed by 2 to 4 years. Unlike the girl in the vignette, the appearance of sexual hair and breast development are delayed in patients who have constitutional delay. Individuals who have familial short stature do not experience pubertal delay and have a compatible family history. Finally, although an imperforate hymen is one cause of primary amenorrhea, affected patients have normal pubertal progression and are of normal height

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During the health supervision visit of a 14-year-old female, you find that her thyroid gland is firm, nontender, symmetrically enlarged, mobile, and has a granular texture. The thyroxine level is 5.2 mcg/dL (normal, 5.6 to 11.7 mcg/dL) and the thyroid-stimulating hormone level is 17.5 mIU/mL (normal, 0.2 to 7.6 mIU/mL).

Of the following, the MOST likely diagnosis is:



A.  acute suppurative thyroiditis

B.  Graves disease

C.  Hashimoto thyroiditis

D.  simple colloid goiter

E.   solitary thyroid nodule

Answer

C



The girl presented in the vignette has a goiter, borderline low thyroxine (T4) concentration, and elevated thyroid-stimulating hormone (TSH) concentration, suggesting hypothyroidism. Hashimoto thyroiditis, also known as chronic lymphocytic thyroiditis, is the most common cause of goiter in the pediatric age group. It is an autoimmune disorder in which lymphocytes and plasma cells infiltrate the thyroid gland, resulting in enlargement and damage to thyroid cells through cytotoxic mechanisms. Most patients present with either a euthyroid goiter or hypothyroidism without goiter; transient hyperthyroidism occurs occasionally.

            In patients who have a goiter, T4 and TSH are measured to identify possible hypothyroidism. If signs of hyperthyroidism are present, a triiodothyronine (T3) measurement also is obtained. Although most patients who have Hashimoto thyroiditis have circulating thyroid antibodies (eg, antithyroglobulin, antimicrosomal antibody [thyroid peroxidase]), these antibodies are not specific for the disease. In the rare case of diagnostic uncertainty, Hashimoto thyroiditis can be confirmed by fine-needle biopsy.

            The natural history of Hashimoto thyroiditis is variable; many individuals remain euthyroid for years, while others develop hypothyroidism. Occasionally there may be spontaneous recovery. Patients who have a euthyroid goiter sometimes are treated with thyroid hormone to reduce the size of the gland. Those who have evidence of hypothyroidism or an elevated TSH concentration require thyroid replacement.

            Acute suppurative thyroiditis is an uncommon disorder caused by infection with Streptococcus pyogenes, S pneumoniae, or Staphylococcus aureus. Patients present with the abrupt onset of anterior neck pain, fever, and toxicity. Physical examination reveals marked tenderness to palpation of the anterior neck and swelling that is nonmobile and sometimes fluctuant.

            Although patients who have Graves disease have thyroid enlargement, they exhibit symptoms and signs of hyperthyroidism, including weight loss, deteriorating school performance, poor concentration, nervousness, heat intolerance, tachycardia, tremor, or exophthalmos. The serum T4 and T3 concentrations are elevated, and TSH is suppressed.

            A simple colloid goiter generally presents as diffuse enlargement of the thyroid gland in a patient who is clinically euthyroid. Results of thyroid function tests are normal, and thyroid antibodies are absent.

            A solitary thyroid nodule is a discrete, localized enlargement of the thyroid gland. It must be distinguished from a diffusely enlarged gland and nonthyroid masses such as lymph nodes and dermoid cysts. Because a solitary thyroid nodule may be malignant, all affected patients should be referred to a pediatric endocrinologist for additional evaluation. Thyroid function tests should be performed, but results usually are normal. Ultrasonography may be useful in the diagnosis of nodules.


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Q 3



A 12-year-old girl is at the 5th percentile for height. She is an otherwise healthy child. The bone age is greater than two standard deviations below the chronologic age.

Of the following, the MOST likely cause of this patient's short stature is:



A.  constitutional growth delay

B.  genetic short stature

C.  growth hormone deficiency

D.  hypothyroidism

E.  ulcerative colitis

Answer

A



Assessment of bone age is useful in the diagnosis and treatment of growth disorders. The most frequently used method for assessing bone age, developed by Greulich and Pyle, compares radiographs of the patient’s left hand and wrist with established standards. The criteria for defining a certain bone age vary by gender and race, and separate tables are used for males and females. In general, females have more advanced skeletal maturity than males of the same age. In addition, African-American children have more advanced skeletal maturity than Caucasian children.

            A comparison of bone age with chronologic age allows for assessment of the growth rate. During adolescence, those whose bone ages are advanced relative to their chronologic ages are considered early developers; those who have bone ages that are delayed relative to their chronologic ages are late developers.

            The child described in the vignette most likely has constitutional growth delay. Affected children grow normally in early infancy, but then their growth rate declines. Typically, such children lag 2 to 4 years behind their peers in height age, bone age, and sexual development. Frequently, similar growth patterns can be documented in parents, siblings, and other family members. Most children who have constitutional growth delay attain normal adult heights when their growth is complete.

            Genetic short stature is a common cause of short stature. Affected children usually have a height at or below the 3rd percentile, but bone age is comparable to chronologic age, and growth rate is normal.

            Short stature due to hypothyroidism is accompanied by other symptoms, such as constipation, dry skin, cold intolerance, and puffiness (myxedema). Laboratory evaluation reveals elevated thyroid-stimulating hormone and low thyroxine levels. Determination of bone age documents a delay in bone maturation.

            Ulcerative colitis can retard growth and may delay bone development. Many affected children experience poor growth for several years before the onset of the classic symptoms of diarrhea and bloody stools.

            Growth hormone deficiency is a relatively rare cause of short stature that should be considered if other conditions have been excluded. Affected children are often chubby, and boys may have small genitalia. Hypoglycemia may be present. It is associated with a significant delay in bone age compared with chronologic age. The diagnosis can be confirmed by inadequate release of growth hormone following stimulation with arginine or insulin.


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Q 4



You are asked to evaluate an otherwise healthy 17-year-old girl for primary amenorrhea. Her mother and sister began menstruating at age 12. She takes no medications and denies any history of headaches, galactorrhea, nausea, or vomiting. Thelarche occurred at age 13. Her breasts and genitalia are Sexual Maturity Rating (Tanner) stage 5. The bimanual examination reveals a blind vaginal pouch.

Of the following, the study MOST likely to confirm the diagnosis is:



A.  computed tomography of the head

B.  computed tomography of the pelvis

C.  serum estradiol level

D.  serum karyotype

E.   serum prolactin level

Answer

D



Most teens have menarche within 2 to 2.5 years after thelarche or within 1 year of attaining full physical maturity. The presence of primary amenorrhea and normal secondary sexual characteristics at age 17 in the otherwise healthy adolescent girl described in the vignette warrant further evaluation.

            There are numerous causes of primary amenorrhea, but not all need to be considered in a patient who has mature secondary sexual characteristics. Although her external genitalia are phenotypically female, the presence of a blind vaginal pouch is most consistent with the diagnosis of male pseudohermaphroditism. A serum karyotype will confirm this diagnosis.

            Complete testicular feminization is the most common cause of male pseudohermaphroditism (phenotypic female who has 46,XY karyotype and with testes) and results from androgen insensitivity. Not all affected individuals present with ambiguous genitalia because the spectrum of sensitivity is broad. If the receptor to androgens is nonfunctional or absent, the external genitalia will be those of a normal female. The diagnosis is usually delayed until the absence of menses brings the adolescent to medical attention. Internal female genitalia do not form because the müllerian ducts regress under the effects of müllerian inhibiting factor produced by occult male gonads located in the abdomen. However, low levels of gonadal and adrenal estrogens, unopposed by androgens, allow breast development to occur in affected individuals.

            Signs and symptoms of male pseudohermaphroditism are variable, depending on the etiology. As described previously, the phenotypic female may present with primary amenorrhea or an infant may have ambiguous genitalia noted at birth. The otherwise healthy teenager who has androgen insensitivity may have sparse axillary and pubic hair, normal breast development, and a blind vaginal pouch with absence of the ovaries, uterus, and fallopian tubes. Testes and normal male levels of testosterone are present.

            Because the adolescent described in the vignette does not have a central cause of amenorrhea, computed tomography of the head is unnecessary. Furthermore, magnetic resonance imaging is the study of choice to visualize the pituitary gland. Computed tomography of the pelvis may confirm the absence of internal female genitalia, but will not make the diagnosis. A serum estradiol level is unnecessary in the adolescent who has mature breast development. A serum prolactin level is also not indicated because the primary amenorrhea clearly stems from abnormal genital anatomy.

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Q 5



An 18-month-old infant is seen because the mother is concerned that his legs are bowed. The infant was breastfed until 14 months of age. The mother states that her grandfather was very short.

Of the following, laboratory tests are MOST likely to reveal:



A. high circulating parathyroid hormone concentrations

B. inadequate reabsorption of phosphate by the kidney

C. inadequate stimulation of bone resorption by parathyroid hormone

D. low conversion of vitamin D to 25-hydroxylase vitamin D

E. poor gastrointestinal absorption of phosphate

Answer

B



Any child who has hypophosphatemia requires a thorough evaluation because phosphate is essential for energy production and for bone growth and development. The kidney plays a major role in maintaining therapeutic levels of serum phosphate by reabsorbing about 85% to 90% of the filtered phosphate during the first few years of life.

            Ricketsis a general term used to describe bony malformation due to any abnormality in the production or excretion of calcium and phosphate. Any child who has clinical evidence of growth retardation or rickets in the presence of a low serum phosphate level should have serum levels of calcium, parathyroid hormone (PTH), 25-hydroxyvitamin D, and 1,25 dihydroxyvitamin D (1,25(OH)2D) measured. These values will provide clues to the etiology of the growth failure.

            The most common form of inherited rickets is X-linked hypophosphatemic rickets (X-hyp). Children who have this disorder develop hypophosphatemia due to renal wasting of phosphate. The precise mechanism (transport protein abnormality) has not yet been elucidated. Regardless, there is high urinary excretion of phosphate and simultaneous low serum phosphate concentrations. The leak most likely occurs in the renal proximal tubule. Serum calcium and PTH levels are normal. Furthermore, serum 1,25(OH)2D levels are also “normal.” It has been suggested that part of the problem in X-hyp may be due to inadequate stimulation of 1,25(OH)2D synthesis in the kidney in the face of low serum phosphate. Given that one role of 1,25(OH)2D is to stimulate reabsorption of phosphate in the gastrointestinal tract, a compensatory increase in its levels in children who have low serum phosphate levels is expected. Thus, the abnormality in X-hyp appears to be inadequate reabsorption of phosphate by the renal proximal tubule in combination with inappropriate levels of 1,25(OH)2D synthesis by the kidney.

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Q 6



A 12-year-old girl presents with a history of palpitations, problems with sleeping, and recent weight loss despite increased appetite. Significant findings on physical examination include tachycardia, mild exophthalmos, a palpable thyroid, and a tremor.
Of the following, the MOST appropriate initial treatment for this child is:

A. observation and re-evaluation
B. oral methimazole
C. oral thyroxine
D. thyroid ablation with I131
E. thyroidectomy

Answer

B



Therapy for hyperthyroidism includes medical treatment, ablation with I131, and surgery. The most appropriate initial treatment is oral therapy with methimazole, carbimazole, or propylthiouracil. Methimazole often is preferred because maintenance doses can be administered once daily. Minor complications of medical therapy include pruritus, fever, rash, and urticaria. Suppressive medical therapy is recommended for at least 12 to 24 months before the drug gradually is discontinued. 

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Q 7



A 6-year-old girl who has type 1 diabetes presents with a 2-day history of fever, malaise, and diarrhea. She is well hydrated, and findings on physical examination are normal. The urine is positive for ketones, and the blood glucose level is 14.4 mmol/L (260 mg/dL). Electrolyte levels, including bicarbonate, are normal.
In addition to providing supplemental insulin as needed, the MOST appropriate management of this patient is to:



A. hospitalize her immediately

B.  instruct her to check her blood glucose once a day

C. instruct her to check her urine for ketones once a day

D. instruct her to decrease her total caloric intake

E.  instruct her to drink large amounts of sugar-free liquids
Answer

E

Children who have diabetes need to be monitored closely during an intercurrent illness. The primary goal for management of diabetes during an illness is to prevent the occurrence of hypoglycemia and diabetic ketoacidosis and the need for hospitalization. When diabetic children are sick, they almost always require some extra insulin in addition to their routine dose. Supplemental insulin often can be administered as a dose of subcutaneous regular insulin equivalent to approximately 10% of the total daily dose; this may be repeated every 2 to 4 hours until ketosis is cleared.

 monitoring of blood glucose values.
            It is recommended that children who have diabetes ideally check blood glucose levels every 4 to 6 hours on sick days. In addition, checking urine for ketones every 4 to 6 hours on sick days will alert children if they begin to spill ketones in their urine, indicating ketoacidosis. Ketones indicate insulin deficiency or stress-related insulin resistance with inadequate compensation using extra insulin.

            Drinking large amounts of sugar-free liquids should help prevent dehydration. Young children should ingest approximately 3 to 6 oz/hr; adolescents should drink 6 to 8 oz/hr. In addition, maintaining or increasing total caloric intake should speed recovery. If a child cannot tolerate liquids, and vomiting persists, he or she may need to be evaluated in an emergency department or admitted to a hospital for administration of intravenous fluids and glucose and careful monitoring of electrolytes. Parents should be instructed to seek medical assistance if the child has signs or symptoms of severe dehydration, persistent vomiting or diarrhea, severe abdominal pain, or any respiratory difficulties

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Q 8


A newborn whose birthweight was 1,100 g and estimated gestational age at birth was 30 weeks is receiving mechanical ventilation, intravenous nutrition, and antibiotic therapy for suspected sepsis at 10 days of postnatal life. Results from routine screening for thyroid function reveal a low serum total thyroxine (T4) concentration and a low serum thyroid-stimulating hormone (TSH) concentration.

Of the following, the MOST accurate statement regarding thyroid function in this infant is that:



A. hypothalamic-pituitary-thyroid immaturity is largely hypothalamic in origin

B. hypothyroxinemia of prematurity warrants brief thyroid replacement therapy
C. nonthyroidal illness decreases the serum concentration of reverse triiodothyronine
D. thyroid hormone surge immediately following birth is absent
E. topical application of iodine-containing antiseptics is a common cause of primary 

Answer

A


The principal cause of hypothyroxinemia of prematurity is immaturity of the hypothalamic portion of the hypothalamus-pituitary-thyroid axis. 



The resulting lack of endogenous production of the hypothalamic hormone, thyrotropin-releasing hormone (TRH), leads to a low serum concentration of both thyroid-stimulating hormone (TSH) and thyroxine (T4), as reported for the infant in the vignette. In preterm infants, exogenous administration of TRH causes a prompt increase in serum concentration of TSH and a secondary increase in serum concentration of T4, which suggests that both the pituitary and the thyroid glands are normally responsive to the hypothalamic hormone.

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Q 9



You are caring for a 12-year-old boy who has been receiving 125 mcg/d of thyroxine for
treatment of congenital hypothyroidism. He has been growing well and doing well in school. His
thyroxine and thyroid-stimulating hormone (TSH) values have been normal and stable for the
past year. At this visit, you measure a free thyroxine (fT4) concentration of 2.5 ng/dL (32.3
pmol/L) (normal, 0.8 to 2.0 ng/dL [10.3 to 25.7 pmol/L]) and a TSH concentration of 12.6 mIU/L
(12.6 mU/L) (normal, 0.5 to 5.0 mIU/L [0.5 to 5.0 mU/L]).

Of the following, the MOST likely reason for these abnormal laboratory study results is


A. patient nonadherance with therapy

B. pubertal thyroid hormone resistance
C. pubertal TSH resistance
D. resetting of normal TSH concentrations due to in utero hypothyroidism
E. substitution of generic thyroxine by pharmacy

Answer


A


The child described in the vignette has an elevation in both his free thyroxine (fT4) and thyroidstimulating
hormone (TSH) values. The most common reason for these findings in an individual
taking thyroid hormone is medication mismanagement. Although it is reasonable to take a double
dose of medication if the thyroxine was forgotten the day before, both the TSH and the fT4 are
likely to be elevated for up to 7 days because of discordance between thyroxine administration
and TSH suppression. Because medication mismanagement is so common, TSH alone never
should be used to monitor the need for changes in thyroxine dosage.

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Q 10:


You are discussing treatment choices with the family of a 13-year-old girl in whom you have just
diagnosed hyperthyroidism. You include antithyroid drug therapy, surgery, and radioactive iodine
treatment in your discussion. They choose antithyroid drug therapy with methimazole for initial
therapy.
Of the following, the MOST likely adverse effect of this therapy is

A. agranulocytosis
B. cholestatic jaundice
C. headache
D. hematuria
E. rash

Answer

E


The most common adverse effects of the thionamide antithyroid drugs such as methimazole and propylthiouracil are rashes, arthritis, and arthralgias, which are considered minor complications. Headache is not a common adverse effect of these agents.

 More severe complications are relatively rare and include hepatitis. Liver involvement with methimazole is
reversible, but propylthiouracil-induced hepatitis may result in liver failure. Neutropenia may be
seen with either methimazole or propylthiouracil. It is important to obtain a baseline white blood
cell count before starting therapy because thyrotoxicosis itself may be associated with
neutropenia. Agranulocytosis is a rare complication, usually occurring in older individuals within
the first few months of therapy, and sometimes is irreversible. It may be dose-dependent.
Hematuria is an unusual complication of therapy with these drugs and results from systemic
vasculitis. Vasculitis is more common with propylthiouracil and rarely reported with methimazole

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