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ABP Pediatric Endocrinology study materials
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ABP Pediatric Endocrinology practice questions

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Question 1Growth, growth hormone, and short stature

Short stature in a child is conventionally defined by which criterion?

  1. A predicted adult height below the mid-parental height
  2. Height more than 2 SD below the mean for age Correct answer.
  3. Weight more than 2 SD below the mean for age and sex
  4. Height below the 25th percentile for age and sex

Explanation

Short stature is defined statistically as a height more than 2 SD below the mean for age and sex, which corresponds roughly to the 3rd percentile. This threshold identifies children who merit growth evaluation, but it does not by itself indicate pathology. Serial growth velocity is often more informative than a single height measurement.

Question 2Growth, growth hormone, and short stature

Which chromosomal disorder is the most common chromosomal cause of short stature in girls?

  1. Trisomy 21
  2. Turner syndrome Correct answer.
  3. Klinefelter syndrome
  4. Noonan syndrome

Explanation

Turner syndrome results from complete or partial loss of one X chromosome and is the most common chromosomal cause of short stature in girls. Short stature affects nearly all affected girls and may be recognized before other stigmata. Gonadal dysgenesis produces elevated gonadotropins and absent or incomplete puberty.

Question 3Growth, growth hormone, and short stature

A 7-year-old presents with declining growth velocity, weight gain, constipation, and a delayed bone age. TSH is elevated and free T4 is low. Which statement about the growth disturbance is most accurate?

  1. The short stature is unrelated to the thyroid abnormality
  2. Growth hormone therapy is the first-line treatment
  3. Bone age is typically advanced rather than delayed
  4. Adequate levothyroxine replacement usually permits catch-up growth Correct answer.

Explanation

Untreated primary hypothyroidism slows linear growth, delays bone maturation, and blunts GH secretion and IGF-1 generation. Restoring euthyroidism with levothyroxine typically produces catch-up growth while the epiphyses remain open. Growth hormone is not indicated when the underlying deficiency is thyroid hormone.

Question 4Growth, growth hormone, and short stature

A 3-year-old has short limbs with proximal shortening, a relatively long trunk, frontal bossing, and age-appropriate developmental milestones. Which diagnosis best explains these findings?

  1. Achondroplasia Correct answer.
  2. Turner syndrome
  3. Growth hormone deficiency
  4. Constitutional delay of growth

Explanation

Achondroplasia is caused by activating FGFR3 variants and produces disproportionate short stature with rhizomelic limb shortening, macrocephaly, and frontal bossing. Intelligence and development are usually normal. Growth hormone deficiency and constitutional delay cause proportionate short stature.

Question 5Growth, growth hormone, and short stature

A 6-year-old with a fall in growth velocity has abdominal bloating, intermittent diarrhea, and iron-deficiency anemia. Which initial test is most likely to establish the cause of the growth failure?

  1. IgA tissue transglutaminase antibody Correct answer.
  2. Overnight serial GH sampling
  3. GH stimulation testing with two provocative agents
  4. IGF-1 measurement

Explanation

Celiac disease causes malabsorption, iron deficiency, and growth failure, and serologic screening with IgA tissue transglutaminase is the appropriate first step; total IgA should also be checked because IgA deficiency can cause a false-negative result. Small bowel biopsy confirms the diagnosis before a gluten-free diet is started. GH testing is premature until nutritional and gastrointestinal causes are excluded.

Question 6Growth, growth hormone, and short stature

A bone age radiograph in a child with short stature most directly provides information about which of the following?

  1. The GH concentration at the moment of the radiograph
  2. Skeletal maturation and remaining growth potential Correct answer.
  3. Chronological age at the time of the radiograph
  4. Dietary calcium intake over the preceding year

Explanation

Bone age assesses ossification of the carpal and phalangeal epiphyses and serves as a marker of skeletal maturation. Comparing bone age with chronological age helps distinguish constitutional delay from precocious puberty and estimates remaining growth potential. It does not directly measure hormone levels or nutritional intake.

Question 7Growth, growth hormone, and short stature

A boy's father is 170 cm tall and his mother is 158 cm tall. Using the mid-parental height method, what is this boy's predicted adult height?

  1. 164.0 cm
  2. 157.5 cm
  3. 177.0 cm
  4. 170.5 cm Correct answer.

Explanation

For boys, mid-parental height is calculated as (father's height + mother's height + 13 cm) / 2. Here (170 + 158 + 13) / 2 = 170.5 cm. For girls the same formula is used but 13 cm is subtracted instead of added.

Question 8Growth, growth hormone, and short stature

A 13-year-old boy is at the 2nd percentile for height, has a bone age of 10 years, no pubic hair, and a father who reached puberty at age 16. His growth velocity is normal for bone age. Which management is most appropriate?

  1. Observation and growth monitoring Correct answer.
  2. Perform GH stimulation testing
  3. Start growth hormone therapy
  4. Obtain a pituitary MRI

Explanation

Constitutional delay of growth and puberty is characterized by a bone age that lags behind chronological age, a family history of late puberty, and normal growth velocity for bone age. Growth and puberty usually occur spontaneously, so observation with serial measurements is appropriate. GH therapy and pituitary imaging are reserved for children with evidence of deficiency or intracranial pathology.

Question 9Growth, growth hormone, and short stature

Which statement about GH provocation testing in the evaluation of short stature is most accurate?

  1. The peak GH response is unaffected by obesity
  2. Provocation testing is required before treating idiopathic short stature
  3. A single random GH value above 10 ng/mL excludes deficiency
  4. Random GH levels are rarely diagnostic because secretion is pulsatile Correct answer.

Explanation

GH is released in nocturnal and post-exercise pulses, so a random daytime value carries little diagnostic information. Provocation tests use agents such as arginine, clonidine, or glucagon and may require sex steroid priming in peripubertal children. Obesity blunts the GH response and can produce a falsely low peak.

Question 10Growth, growth hormone, and short stature

Which statement best describes the role of IGF-1 measurement in evaluating a child with short stature?

  1. IGF-1 levels rise in malnutrition
  2. A low IGF-1 level alone is sufficient to establish GH deficiency
  3. It reflects integrated GH secretion and varies with age and nutrition Correct answer.
  4. IGF-1 does not change during puberty

Explanation

IGF-1 is produced mainly under GH stimulation and has a longer half-life than GH, so it provides an integrated index of GH secretion. Reference ranges must be age- and sex-specific because levels rise during puberty and fall with malnutrition and hypothyroidism. Because values overlap with those of normal children, a low level supports but does not prove GH deficiency.

Question 11Growth, growth hormone, and short stature

A boy born at 36 weeks' gestation with a birth weight below the 3rd percentile remains short at age 4 with no catch-up growth. Which statement is most accurate?

  1. Children born small for gestational age never respond to GH therapy at any age
  2. Catch-up usually occurs by age 2; persistent short stature may warrant GH Correct answer.
  3. Short stature in SGA always indicates GH deficiency
  4. Catch-up growth should be complete by 6 months of age

Explanation

Most children born small for gestational age show catch-up growth during the first 2 years. Those who remain short beyond about 4 years may be treated with GH, which improves adult height. GH deficiency is not the usual mechanism; the disorder reflects prenatal growth restraint and relative GH resistance.

Question 12Growth, growth hormone, and short stature

A 7-year-old girl presents with breast development and rapid growth. Her predicted adult height is reduced mainly because of which mechanism?

  1. Low thyroid hormone levels
  2. Estrogen accelerates bone maturation and epiphyseal fusion Correct answer.
  3. Inadequate caloric intake
  4. Impaired GH secretion

Explanation

Early estrogen exposure accelerates skeletal maturation, so the child may be tall for age initially but fuses the epiphyses prematurely. The result is a shorter adult height despite early rapid growth. Treatment with a GnRH agonist slows bone maturation and helps preserve growth potential.

Question 13Growth, growth hormone, and short stature

A 10-year-old receiving long-term oral prednisone for nephrotic syndrome has a falling growth velocity. Which mechanism best explains this finding?

  1. Increased pituitary GH pulse amplitude
  2. GH suppression and direct inhibition of chondrocytes Correct answer.
  3. Stimulation of epiphyseal cartilage expansion
  4. Increased IGF-1 receptor density in growth plate cartilage

Explanation

Exogenous glucocorticoids reduce hypothalamic GHRH and pituitary GH secretion, decrease IGF-1 bioactivity, and directly inhibit growth plate chondrocytes. The net effect is growth failure with delayed bone age. Minimizing steroid dose and using steroid-sparing agents are key preventive measures.

Question 14Growth, growth hormone, and short stature

Which factor contributes most to growth failure in children with chronic kidney disease?

  1. Increased caloric intake
  2. Early onset of puberty alone is the principal driver
  3. GH resistance and low IGF-1 bioactivity Correct answer.
  4. Excessive GH secretion

Explanation

Chronic kidney disease produces GH resistance, reduced IGF-1 bioactivity, metabolic acidosis, renal osteodystrophy, and malnutrition, all of which impair growth. Supraphysiologic doses of GH can overcome part of this resistance and improve height velocity. Optimal management also addresses acidosis, nutrition, and mineral metabolism.

Question 15Growth, growth hormone, and short stature

A boy has short stature, a webbed neck, widely spaced nipples, and pulmonary valve stenosis. His karyotype is normal. Which diagnosis is most likely?

  1. Noonan syndrome Correct answer.
  2. Turner syndrome
  3. Achondroplasia
  4. Laron syndrome

Explanation

Noonan syndrome is an autosomal dominant RASopathy, commonly caused by PTPN11 variants, that shares Turner-like features including short stature, webbed neck, and congenital heart disease, especially pulmonary stenosis. Unlike Turner syndrome, it affects both sexes and the karyotype is normal. Growth hormone therapy may improve height in some affected children.

Question 16Growth, growth hormone, and short stature

A child with GH deficiency is started on recombinant GH. Which measurement is most useful for monitoring the response and safety of therapy?

  1. Bone age every 3 months
  2. Serum calcium
  3. Random GH level
  4. IGF-1 level Correct answer.

Explanation

IGF-1 reflects the tissue effect of GH and is used to titrate dosing, with the goal of keeping levels within the normal range for age and sex. Persistently high IGF-1 suggests overdosing and may increase the risk of adverse effects. Growth velocity and bone age are monitored periodically but not every 3 months.

Question 17Growth, growth hormone, and short stature

A child has severe short stature, high baseline GH, low IGF-1, and no rise in IGF-1 after several days of exogenous GH. Which defect best explains these findings?

  1. IGF-1 receptor mutation
  2. Bioinactive GH molecule
  3. Pituitary GH deficiency
  4. GH receptor mutation Correct answer.

Explanation

A GH receptor defect (Laron syndrome) produces GH resistance: GH is elevated, IGF-1 is low, and IGF-1 does not increase with exogenous GH. Treatment requires IGF-1 itself rather than GH. Pituitary deficiency and bioinactive GH both respond to exogenous GH with a rise in IGF-1.

Question 18Growth, growth hormone, and short stature

A 6-year-old with severe growth failure shows bizarre eating and drinking behaviors and poor social interaction. During a hospitalization, GH responses to provocation are normal and growth improves. Which explanation is most likely?

  1. Laron syndrome
  2. Constitutional delay of growth
  3. Reversible stress-related GH suppression Correct answer.
  4. Classic pituitary growth hormone deficiency

Explanation

Psychosocial short stature results from chronic stress and neglect, with hypercortisolism and reversible suppression of GH secretion. Growth and GH responses often normalize when the child is placed in a supportive environment. The history of disordered eating and social withdrawal supports this diagnosis.

Question 19Growth, growth hormone, and short stature

A 10-year-old presents with rapid growth, tall stature, headaches, and a GH level that does not suppress during an oral glucose tolerance test. Which cause is most likely?

  1. GH-secreting pituitary adenoma Correct answer.
  2. Primary hypothyroidism
  3. Exogenous obesity
  4. Constitutional tall stature

Explanation

Growth hormone excess before epiphyseal fusion causes gigantism, and failure of GH to suppress during oral glucose loading is the hallmark. Elevated IGF-1 and a pituitary adenoma on MRI usually confirm the diagnosis. Early recognition matters because untreated disease causes extreme adult height and metabolic complications.

Question 20Growth, growth hormone, and short stature

Which statement about GH therapy for idiopathic short stature is most accurate?

  1. It is contraindicated in every child with idiopathic short stature
  2. It should be started only after puberty has begun
  3. It gives a modest average height gain with variable response Correct answer.
  4. It reliably brings adult height into the normal range for all treated children

Explanation

GH treatment in idiopathic short stature increases adult height by a modest average amount, generally a few centimeters, and the response varies widely between children. Because the diagnosis is one of exclusion, other causes of short stature must be ruled out first. Counseling should cover realistic expectations and the burden of daily injections.

Question 21Hypothalamic and pituitary disorders

A 7-year-old with short stature and slow growth is being screened for growth hormone deficiency. Because growth hormone is secreted in pulses, which measurement is most useful as an initial screening test?

  1. A random growth hormone level
  2. Peak growth hormone after exercise
  3. IGF-1 and IGFBP-3 Correct answer.
  4. 24-hour urine growth hormone

Explanation

Growth hormone is released in bursts, so a random level is often low even in healthy children. IGF-1 and IGFBP-3 are stable markers that reflect integrated growth hormone action. Provocative testing is reserved for confirming the diagnosis when screening results suggest deficiency.

Question 22Hypothalamic and pituitary disorders

Central diabetes insipidus results from deficient secretion of which hormone?

  1. Cortisol
  2. Atrial natriuretic peptide
  3. Aldosterone
  4. Arginine vasopressin Correct answer.

Explanation

Central diabetes insipidus is caused by inadequate production or release of arginine vasopressin from the posterior pituitary. Without vasopressin, the kidneys cannot concentrate urine, leading to polyuria and polydipsia. Nephrogenic diabetes insipidus instead reflects renal resistance to vasopressin.

Question 23Hypothalamic and pituitary disorders

In girls, central precocious puberty is defined by the onset of breast development before what age?

  1. 9 years
  2. 7 years
  3. 8 years Correct answer.
  4. 6 years

Explanation

In girls, breast development before 8 years is the conventional threshold for precocious puberty. In boys, testicular enlargement before 9 years is the corresponding threshold. The distinction matters because evaluation and treatment differ by sex and pubertal sign.

Question 24Hypothalamic and pituitary disorders

A newborn boy has micropenis, cryptorchidism, and hypoglycemia. Deficiency of which pituitary hormones most directly explains the micropenis?

  1. Thyroid-stimulating hormone
  2. LH and FSH Correct answer.
  3. Prolactin
  4. Growth hormone

Explanation

Fetal luteinizing hormone and follicle-stimulating hormone drive testosterone production, which is needed for normal penile and testicular development. Congenital hypopituitarism can therefore present with micropenis and cryptorchidism. Growth hormone and ACTH deficiency contribute more to hypoglycemia than to penile growth.

Question 25Hypothalamic and pituitary disorders

A child presents with headaches, bitemporal hemianopsia, and growth failure. MRI shows a calcified cystic sellar and suprasellar mass. What is the most likely diagnosis?

  1. Germinoma
  2. Craniopharyngioma Correct answer.
  3. Pituitary macroadenoma
  4. Prolactinoma

Explanation

Craniopharyngioma is an epithelial tumor that typically arises in the sellar or suprasellar region and often contains cysts and calcification. It can compress the optic chiasm and pituitary, causing visual field loss and endocrine deficits. This combination of calcified cystic mass with visual and growth problems is characteristic.

Question 26Hypothalamic and pituitary disorders

A child has a low free T4 concentration and a low-normal TSH concentration. Which diagnosis best fits this pattern?

  1. Graves disease
  2. Thyroid hormone resistance
  3. Primary hypothyroidism
  4. Central hypothyroidism Correct answer.

Explanation

Low free T4 with an inappropriately low or normal TSH indicates failure of the hypothalamic-pituitary-thyroid axis. Primary hypothyroidism would produce an elevated TSH because the thyroid gland is failing. Central hypothyroidism requires replacement guided by free T4 rather than TSH alone.

Question 27Hypothalamic and pituitary disorders

A 7-year-old girl has breast development and pubic hair. Which result on GnRH stimulation testing supports central precocious puberty?

  1. Pubertal LH response Correct answer.
  2. Suppressed LH after GnRH
  3. No rise in LH
  4. Elevated FSH only

Explanation

Central precocious puberty is GnRH-dependent, so GnRH stimulation produces a pubertal pattern of LH release. Peripheral precocious puberty is driven by sex steroids outside the hypothalamic-pituitary axis and typically suppresses LH. The LH response therefore helps distinguish central from peripheral causes.

Question 28Hypothalamic and pituitary disorders

A child with polyuria and polydipsia undergoes a water deprivation test. After desmopressin, urine osmolality rises substantially. What is the diagnosis?

  1. Central diabetes insipidus Correct answer.
  2. Primary polydipsia
  3. Osmotic diuresis
  4. Nephrogenic diabetes insipidus

Explanation

In central diabetes insipidus, the kidneys respond normally to exogenous desmopressin, so urine osmolality rises as water is reabsorbed. In nephrogenic diabetes insipidus, the renal response remains poor. Primary polydipsia usually shows some concentration with water deprivation rather than the marked desmopressin response of central diabetes insipidus.

Question 29Hypothalamic and pituitary disorders

Which triad is most consistent with septo-optic dysplasia?

  1. Anosmia, hypogonadism, renal agenesis, and situs inversus
  2. Cleft palate, micrognathia, growth hormone deficiency, and developmental delay
  3. Optic nerve hypoplasia, midline defects, and hypopituitarism Correct answer.
  4. Hydrocephalus, precocious puberty, obesity, and temperature instability

Explanation

Septo-optic dysplasia classically combines optic nerve hypoplasia, midline brain abnormalities such as absent septum pellucidum, and hypopituitarism. Affected children may present with visual impairment, nystagmus, hypoglycemia, or growth failure. The combination of eye and midline brain findings should prompt endocrine evaluation.

Question 30Hypothalamic and pituitary disorders

A 15-year-old girl with amenorrhea has elevated prolactin and a 6-mm pituitary adenoma. What is the preferred initial treatment?

  1. Dopamine agonist therapy Correct answer.
  2. Transsphenoidal surgical resection
  3. Cranial irradiation
  4. Observation only

Explanation

Prolactinomas respond well to dopamine agonists such as cabergoline, which lower prolactin and usually shrink the tumor. Surgery is generally reserved for medication resistance, intolerance, or urgent compression. Irradiation is not first-line therapy for a small prolactinoma.

Question 31Hypothalamic and pituitary disorders

A child develops polyuria immediately after resection of a craniopharyngioma. Which management is most appropriate for suspected central diabetes insipidus?

  1. Hypertonic saline infusion
  2. Fluid restriction alone
  3. Desmopressin and monitoring Correct answer.
  4. Immediate oral vasopressin

Explanation

Postoperative central diabetes insipidus is treated with desmopressin while fluid intake and serum sodium are monitored closely. Careful monitoring helps avoid water intoxication and hypernatremia, especially because the disorder can fluctuate after surgery. Hypertonic saline is used for severe hypernatremia, not as routine treatment of diabetes insipidus.

Question 32Hypothalamic and pituitary disorders

A 15-year-old boy has delayed puberty and anosmia. Which diagnosis is most likely?

  1. Kallmann syndrome Correct answer.
  2. Klinefelter syndrome
  3. Isolated growth hormone deficiency
  4. Constitutional delay of growth

Explanation

Kallmann syndrome is hypogonadotropic hypogonadism caused by failure of GnRH neurons to migrate normally, and it is associated with anosmia. Constitutional delay does not cause anosmia, and Klinefelter syndrome is a primary testicular disorder with elevated gonadotropins. Isolated growth hormone deficiency affects stature rather than smell and pubertal timing.

Question 33Hypothalamic and pituitary disorders

Which MRI triad is characteristic of pituitary stalk interruption syndrome?

  1. Empty sella, optic atrophy, corpus callosum agenesis, and hydrocephalus
  2. Enlarged pituitary gland, thickened stalk, and a sellar cyst
  3. Bilateral adrenal hyperplasia, sellar mass, stalk thickening, and calcification
  4. Absent stalk, ectopic posterior pituitary, small anterior pituitary Correct answer.

Explanation

Pituitary stalk interruption syndrome shows an absent or very thin pituitary stalk, an ectopic posterior pituitary bright spot, and a hypoplastic anterior pituitary. It is a recognized cause of congenital growth hormone deficiency and combined pituitary hormone deficiency. The MRI findings reflect abnormal embryonic development of the pituitary region.

Question 34Hypothalamic and pituitary disorders

A child with central adrenal insufficiency is suspected. Which laboratory pattern is expected?

  1. Low ACTH and low cortisol Correct answer.
  2. High ACTH and low aldosterone
  3. Low ACTH and high cortisol
  4. High ACTH and high cortisol

Explanation

Central adrenal insufficiency reflects deficient ACTH production, so both ACTH and cortisol are low or inappropriately normal. Aldosterone is usually preserved because it is regulated mainly by the renin-angiotensin system. Primary adrenal insufficiency instead produces high ACTH with low cortisol and often low aldosterone.

Question 35Hypothalamic and pituitary disorders

An MRI in an asymptomatic child with short stature shows cerebrospinal fluid filling the sella and a flattened pituitary gland. What does this finding most likely represent?

  1. Lymphocytic hypophysitis
  2. Empty sella Correct answer.
  3. Pituitary macroadenoma
  4. Craniopharyngioma

Explanation

An empty sella describes herniation of cerebrospinal fluid into the sella with flattening of the pituitary gland. It is often incidental and not a tumor, although it can be associated with pituitary hormone deficiencies. The finding should prompt endocrine testing only when clinically indicated.

Question 36Hypothalamic and pituitary disorders

Which medication commonly causes hyperprolactinemia in adolescents by blocking dopamine D2 receptors?

  1. Levothyroxine
  2. Amoxicillin
  3. Risperidone Correct answer.
  4. Metformin

Explanation

Risperidone and other antipsychotics can block dopamine D2 receptors in the pituitary, removing tonic inhibition of prolactin secretion. This produces hyperprolactinemia that may cause gynecomastia, galactorrhea, or amenorrhea. Metformin, levothyroxine, and amoxicillin do not act through this mechanism.

Question 37Hypothalamic and pituitary disorders

A child with combined pituitary hormone deficiency has growth hormone, TSH, prolactin, and gonadotropin deficiency. Which gene mutation is most classically associated with this pattern?

  1. GH1
  2. GHRHR
  3. PROP1 Correct answer.
  4. POU1F1

Explanation

PROP1 mutations cause combined pituitary hormone deficiency involving growth hormone, TSH, prolactin, and gonadotropins, with ACTH deficiency sometimes evolving later. POU1F1 mutations typically affect growth hormone, prolactin, and TSH but spare gonadotropins. GH1 and GHRHR defects cause isolated growth hormone deficiency or growth hormone resistance rather than this combined pattern.

Question 38Hypothalamic and pituitary disorders

A child with severe short stature has high growth hormone, low IGF-1, and low IGFBP-3. Which diagnosis is most likely?

  1. Primary hypothyroidism
  2. Constitutional delay of growth
  3. Growth hormone insensitivity Correct answer.
  4. Growth hormone deficiency

Explanation

Growth hormone insensitivity, such as Laron syndrome from a growth hormone receptor defect, produces high growth hormone but low IGF-1 and IGFBP-3 because the hormone cannot activate its receptor. These children respond poorly to growth hormone and may be treated with IGF-1. Growth hormone deficiency would show low growth hormone rather than high levels.

Question 39Hypothalamic and pituitary disorders

A 12-year-old girl has weight gain, hypertension, striae, and impaired growth. Which finding best supports Cushing disease rather than an adrenal tumor?

  1. Low ACTH
  2. Suppressed cortisol after dexamethasone
  3. High DHEAS
  4. Elevated ACTH, no diurnal rhythm Correct answer.

Explanation

Cushing disease is an ACTH-secreting pituitary adenoma, so ACTH is elevated and the normal diurnal fall in cortisol is lost. An adrenal tumor usually suppresses ACTH because cortisol feedback is intact at the pituitary. High-dose dexamethasone suppression may occur in Cushing disease but not in ectopic ACTH or adrenal tumors.

Question 40Hypothalamic and pituitary disorders

A child has severe obesity, hyperphagia, and rapid weight gain after surgery near the hypothalamus. Which mechanism best explains this?

  1. Cortisol deficiency
  2. Primary hypothyroidism
  3. Excess growth hormone secretion and insulin resistance
  4. Loss of hypothalamic satiety signaling Correct answer.

Explanation

Hypothalamic injury can damage satiety centers and disrupt autonomic and hormonal regulation of energy balance, producing hyperphagia and rapid weight gain. This is often called hypothalamic obesity and is not simply a matter of overeating. It is a recognized complication after surgery for tumors such as craniopharyngioma.

Question 41Thyroid disorders

A newborn's filter-paper screen shows an elevated TSH. What is the most appropriate next step?

  1. Obtain a thyroid ultrasound as the confirmatory test
  2. Repeat the newborn screen at 6 months of age
  3. Measure serum free T4 and TSH to confirm Correct answer.
  4. Begin levothyroxine without any further testing

Explanation

An elevated filter-paper TSH is only a screening result, so it must be confirmed with serum free T4 and TSH, which also grade severity. Levothyroxine is started promptly once the confirmatory sample has been drawn, not before any serum testing. Definitive testing must never be deferred for months, because untreated congenital hypothyroidism impairs brain development.

Question 42Thyroid disorders

What is the most common cause of congenital hypothyroidism in iodine-sufficient countries?

  1. Thyroid dysgenesis Correct answer.
  2. Maternal antithyroid drug use
  3. Dietary iodine deficiency
  4. Biallelic TSH receptor mutations

Explanation

Thyroid dysgenesis, which includes agenesis, hypoplasia, and ectopic placement of the gland, accounts for roughly 80 to 85 percent of congenital hypothyroidism. Inborn errors of hormone synthesis rank second and typically produce a goiter. Iodine deficiency is an important global cause but is uncommon where salt is iodized.

Question 43Thyroid disorders

Which initial levothyroxine dose is recommended for a term infant with confirmed congenital hypothyroidism?

  1. 1-2 mcg/kg/day
  2. 3-5 mcg/kg/day
  3. 10-15 mcg/kg/day Correct answer.
  4. 25-30 mcg/kg/day

Explanation

Infants require a high initial dose of about 10 to 15 mcg/kg/day to restore thyroid hormone rapidly and protect cognitive development. Lower doses delay normalization of free T4 and lengthen the period of brain exposure to deficiency. Doses far above this range cause over-replacement with craniosynostosis and behavioral problems.

Question 44Thyroid disorders

Which antibody is the most sensitive serological marker of Hashimoto thyroiditis in children?

  1. Anti-smooth muscle antibody
  2. Anti-thyroid peroxidase antibody Correct answer.
  3. Anti-nuclear antibody
  4. TSH-receptor stimulating immunoglobulin

Explanation

Anti-thyroid peroxidase antibodies are present in the large majority of children with Hashimoto thyroiditis and are the most sensitive serological marker. Anti-thyroglobulin antibodies occur in a smaller proportion and may be found in healthy children. TSH-receptor antibodies define Graves disease rather than Hashimoto thyroiditis.

Question 45Thyroid disorders

In a healthy child, what effect does a rise in serum thyroid hormone have on the pituitary?

  1. It stimulates pituitary TSH release
  2. It suppresses pituitary TSH release Correct answer.
  3. It has no measurable effect on TSH release
  4. It stimulates hypothalamic TRH release

Explanation

Thyroid hormone feeds back negatively on both the hypothalamus and the pituitary, suppressing TRH and TSH secretion. This closed loop holds free T4 and T3 within a narrow range. Loss of this negative feedback explains the high TSH seen in primary hypothyroidism.

Question 46Thyroid disorders

A newborn whose mother has Graves disease develops tachycardia, poor weight gain, and a goiter at 5 days of age. Which mechanism best explains this?

  1. Transient overproduction of pituitary TSH
  2. Placental transfer of excess maternal levothyroxine
  3. Placental transfer of maternal TSH receptor antibodies Correct answer.
  4. An inherited activating TSH receptor mutation

Explanation

Stimulating TSH receptor antibodies from the mother cross the placenta and drive the fetal and neonatal thyroid. The result is transient neonatal Graves disease that resolves over weeks to a few months as maternal antibody is cleared. Affected infants may need beta-blockade and occasionally a thionamide.

Question 47Thyroid disorders

A 10-year-old girl has a TSH of 7.5 mU/L, a normal free T4, positive anti-thyroid peroxidase antibodies, and no symptoms. How should this pattern be described?

  1. Subclinical hypothyroidism Correct answer.
  2. Overt primary hypothyroidism
  3. Central hypothyroidism
  4. Nonthyroidal illness syndrome

Explanation

Subclinical hypothyroidism is defined by an elevated TSH accompanied by a normal free T4. In children it is most often caused by Hashimoto thyroiditis, and mild asymptomatic cases are frequently monitored with repeat testing rather than treated at once. Treatment is considered when the TSH rises further or symptoms, goiter, or growth effects appear.

Question 48Thyroid disorders

Which set of thyroid function results points to central hypothyroidism?

  1. A normal TSH together with a high free T4 level
  2. A high TSH together with a high free T4 level
  3. A high TSH together with a low free T4 level
  4. A low free T4 with a low or normal TSH Correct answer.

Explanation

In central hypothyroidism the pituitary fails to respond to low thyroid hormone, so free T4 is low while TSH is low or inappropriately normal. A high TSH with a low free T4 instead defines primary hypothyroidism. Once the pattern is recognized, other pituitary hormones and the pituitary region must be evaluated.

Question 49Thyroid disorders

A 6-year-old has a diffusely enlarged goiter, mild hypothyroidism, and a gland that is normally sited on ultrasound. Which category of cause fits best?

  1. Thyroid agenesis with no gland tissue
  2. Pituitary failure with TSH deficiency
  3. Excess iodine intake from supplements
  4. Defective thyroid hormone synthesis Correct answer.

Explanation

A present, normally sited gland that is enlarged and failing to make enough hormone suggests an inborn error of hormone biosynthesis, usually inherited in autosomal recessive fashion. Chronic TSH drive produces the goiter. Thyroid dysgenesis leaves no normally placed gland and does not cause goiter, and central failure would give a low TSH.

Question 50Thyroid disorders

Which antithyroid drug is preferred as initial therapy for a 12-year-old with Graves disease?

  1. Levothyroxine
  2. Methimazole Correct answer.
  3. Potassium iodide alone
  4. Propylthiouracil

Explanation

Methimazole is first-line for Graves disease in children because propylthiouracil carries a risk of fulminant hepatic failure. Propylthiouracil is reserved for thyroid storm, where it also blocks peripheral conversion of T4 to T3, and for the first trimester of pregnancy. Iodide alone and levothyroxine do not control thyrotoxicosis.