Endocrine

Question 1

Which type of diabetes insipidus (DI)—central or nephrogenic—responds to desmopressin therapy?

Answer 1

Central DI
Explanation
Remember that central DI is an ADH deficiency, so giving desmopressin corrects this by increasing urine osmolality and decreasing serum osmolality. Nephrogenic DI is not a deficiency in ADH but is a receptor problem, so giving desmopressin has minimal or no effect.

Question 2

child presents with hypertension. Baseline laboratory tests show that he has hypokalemia and suppressed plasma renin levels.

What is the most likely diagnosis?

Answer 2

Primary hyperaldosteronism
Explanation
Primary hyperaldosteronism is rare in children and includes all disorders in which overproduction of aldosterone occurs that is independent of the renin-angiotensin system. Suspect primary hyperaldosteronism if you see hypertension, hypokalemia, and low plasma renin levels, as in this case.

Question 3

A child was born at the 95th percentile and grew rapidly in the 1st year of life to the 99th percentile. This has continued for his first 5 years. Now in his 6th year, it appears he has slowed to a normal growth rate. He is “clumsy” and has big feet and hands for his age. His bone age is slightly advanced, compatible with his height.

What is the most likely diagnosis?

Answer 3

Sotos syndrome (a.k.a. cerebral gigantism)
Explanation
Sotos syndrome is due to a mutation in one of the NSD1 genes located on 5q35 and is not an endocrine disorder per se. Growth hormone levels are always normal, and affected children typically grow to normal adult heights. Puberty occurs at the normal time or slightly early.

Question 4

A 13-year-old girl presents with the following:

Muscle weakness
Anxiety
Palpitations
Increased appetite
Declining school performance
A thyroid bruit is heard.
TSH is undetectable; FT4 is very high.
What is the most likely diagnosis?

Answer 4

Graves disease
Explanation
Graves disease is the most common cause of thyrotoxicosis in children and adolescents. In addition to the girl’s presenting symptoms, children frequently have cardiac signs. Tremor, excessive perspiration, and rapid tendon reflex relaxation times are also possible. Thyroid size is variable, and the goiter may not be obvious. Children rarely have the eye manifestations and skin changes seen in adults.

Question 5

A 1-year-old boy comes in for a health supervision checkup. He had normal length and weight at birth. You notice that his height is lower than 4 standard deviations below the mean.

What is the most likely diagnosis?

Answer 5

Growth hormone deficiency
Explanation
These infants have normal birth weight and height. Those with severe defects in GH production fall lower than 4 standard deviations below the mean by 1 year of age.

Question 6

What syndrome is associated with anosmia (lack of the sense of smell) and hypogonadism?

Answer 6

Answer
Kallmann syndrome
Explanation
Anosmia (or hyposmia, i.e., reduced ability to smell) is a tip-off for Kallman syndrome. Kallmann syndrome is an isolated deficiency of gonadotropin and affects the hypothalamus (deficiency of GnRH).

Question 7

An 18-year-old girl with negative pregnancy test presents with:

Headache
Amenorrhea
Galactorrhea
What is the most likely diagnosis?

Answer 7

Prolactinoma
Explanation
In adolescents, prolactin-secreting tumors are the most common anterior pituitary tumor. MRI is the best diagnostic tool to find small adenomas. Prolactinomas are generally larger in children, and visual-field defects are common.

Question 8

An 8-year-old boy presents with the following:

Normal growth through 1 year of age
After 1 year of age, growth rate slowed, so that height and weight were < 3rd percentile by 2 years of age.
After 3 years of age, growing at > 5 cm/year
Bone age is delayed by 2 years.
Father is of normal height but was also a “slow grower” early on and “caught up” during puberty—but puberty was delayed by several years compared to peers.
What is the most likely diagnosis?

Answer 8

Constitutional growth delay
Explanation
Constitutional growth delay is a variant of normal growth. Children grow at around the 3rd percentile. When puberty kicks in, they accelerate and reach normal adult heights. Bone age is delayed and mirrors height age in these children. This separates constitutional growth delay from genetic short stature, where bone age is consistent with chronological age—kids who are just genetically short. So, for constitutional growth delay: normal growth velocity, delayed bone age, and family history of delayed puberty.

Question 9

A 17-year-old girl presents with:

Obesity
Acanthosis nigricans
Type 2 diabetes mellitus (DM)
Hirsutism
Secondary amenorrhea
LH to FSH ratio is elevated at 4:1.
Testosterone is elevated.
What is the most likely diagnosis?

Answer 9

Polycystic ovary syndrome (PCOS)
Explanation
PCOS is described as irregular menses with symptoms or biochemical evidence of hyperandrogenism (such as hirsutism and acne) ± bilaterally enlarged polycystic ovaries (confirmed by ultrasound). A high testosterone level with an elevated LH:FSH ratio can be associated with the diagnosis. Additional correlates include obesity, insulin resistance with resulting hyperinsulinemia, and a predisposition to Type 2 DM and cardiovascular disease are common findings in those with PCOS.

Question 10

A 9-year-old boy presents with:

Obesity
Hyperphagia
Light brown to blond hair
Blue eyes with fair skin
Intellectual disability (IQ 20–80)
Small hands and feet
Small penis with history of cryptorchidism
What is the chromosomal deletion, and which parent did the deletion come from?

Answer 10

Deletion of the q11–13 region of chromosome 15 from the father
Explanation
This boy has all the symptoms of Prader-Willi syndrome. This same chromosomal deletion, if it comes from the mother, is Angelman syndrome

Question 11

What is the fasting plasma glucose number that defines the diagnosis of diabetes mellitus (DM)?

Answer 11

Answer
≥ 126 mg/dL
Explanation
The diagnosis can also be made with one of the following:

Classic symptoms of hyperglycemia and a random plasma glucose ≥ 200 mg/dL
A 2-hour plasma glucose ≥ 200 mg/dL during a standard oral glucose tolerance test (OGTT)
A hemoglobin A1c ≥ 6.5%
Any abnormal value must be repeated on a ­subsequent day before the diagnosis is confirmed.

Question 12

A 6-year-old boy presents with the following:

ACTH-independent Cushing syndrome
Blue nevi
Cardiac and skin myxomas
Sexual precocity
What is this complex called?

Answer 12

Answer
Carney complex
Explanation
Carney complex is an autosomal dominant disease that presents as described (with the sexual precocity seen in boys). Frequently, thyroid tumors, pituitary tumors, and melatonin schwannomas are part of the syndrome. Primary pigmented nodular adrenocortical disease, which is part of the Carney complex, is an ACTH-independent cause of Cushing syndrome.

Question 13

A 15-month-old girl presents with isolated breast development. There is no involvement of the adrenal glands and no evidence of body odor, pubic hair, axillary hair, or acne. Height and weight, bone age, and genitals are normal. She has normal estradiol, LH, and FSH levels for her age. There is no known exposure to exogenous estrogen.

What is the most likely diagnosis?

Answer 13

Answer
Premature thelarche
Explanation
Premature thelarche is a diagnosis of exclusion but is a normal variant of normal growth. Thelarche at this age is frequently a benign condition but could be the first sign of true precocious puberty. When clinical evaluation, with or without labs, is otherwise normal, the child can be seen in follow-up. The breast tissue may persist for 3–5 years but can regress during this time

Question 14

Autosomal recessive
Growth restriction
Microcephaly
Ptosis
Anteverted nares
Broad alveolar ridges
Syndactyly of the 2nd and 3rd toes
Severe intellectual disability
Pyloric stenosis
What is the syndrome with these findings?

Answer 14

Smith-Lemli-Opitz syndrome
Explanation
Smith-Lemli-Opitz syndrome is a mutation in one of the enzymes necessary for cholesterol synthesis. Patients with this syndrome have the listed characteristic findings. In addition, genotypic males commonly have genital ambiguity. Müllerian ducts are absent.

Question 15

All children with Type 1 diabetes mellitus (DM) should be screened regularly for what thyroid disorder?

Answer 15

Autoimmune thyroid disease
Explanation
Chronic autoimmune thyroiditis (a.k.a. Hashimoto disease or chronic lymphocytic thyroiditis) is the most common cause of goiter and hypothyroidism in children > 6 years of age. Hashimoto disease occurs in 10–15% of those with Type 1 DM and usually presents about 5 years after the onset of the diabetes

Question 16

A newborn girl presents with virilization and salt wasting.

What is the most likely diagnosis?

Answer 16

21-hydroxylase deficiency
Explanation
21-hydroxylase deficiency is the most common cause of congenital adrenal hyperplasia (95% of cases), and most infants have the salt-wasting + virilizing form. About 25% have only the simple virilizing form (non–salt-wasting). The classic presentation is of an XY infant presenting in adrenal crisis at 2 weeks of age. However, this scenario has become uncommon because of newborn screening initiatives.

Question 17

A 16-year-old boy presents with:

History of adrenal cortex deficiency
New-onset clumsiness
You suspect adrenoleukodystrophy.

The levels of which fatty acid do you expect to be elevated?

Answer 17

Answer
Very high levels of very long-chain fatty acids
Explanation
Adrenoleukodystrophy is caused by a mutation in the ABCD1 gene that encodes a peroxisomal membrane transporter protein and is associated with demyelination of the CNS and primary adrenal insufficiency. Lab findings include very high levels of very long-chain fatty acids in tissues and body fluids due to their lack of breakdown in peroxisomes

Question 18

A boy with 47,XXY is at higher risk for what type of cancer?

Answer 18

Breast cancer
Explanation
Boys with 47,XXY (a.k.a. Klinefelter syndrome) can get breast cancer (same incidence as women). Follow the American Cancer Society breast cancer screening guidelines for women

Question 19

Which has a stronger genetic component, Type 1 or Type 2 diabetes mellitus (DM)?

Answer 19

Answer
Type 2 DM
Explanation
Concordance rates for identical twins are near 100% for Type 2 but only 30–50% for Type 1. However, there is no HLA-type association with Type 2.

Question 20

A 6-year-old boy who was abused and kept locked up in a basement for 6 months presents with:

Irritability
Weakness
Growth restriction
Flared wrists
Genu valgum
Nodules on the ribs
Elevated alkaline phosphatase
Low calcium
Very low 25-OH-vitamin D
What is the likely diagnosis?

Answer 20

Answer
Vitamin D−deficient rickets
Explanation
Vitamin D−deficient rickets is mainly seen in those with limited sun exposure or in babies who are being breastfed by vitamin D–deficient mothers. This differs from familial hypophosphatemic rickets (FHR), the most common form in the U.S. FHR is a kidney disease where the parathyroid hormone level is normal. It is a phosphorus-wasting disease, due to decreased renal tubular resorption of phosphorus.

Question 21

A 10-year-old boy presents with severe HTN. He has headaches, palpitations, abdominal pain, and dizziness. Sweating also occurs. Sometimes his blood pressure is normal, but it is usually sustained elevated.

What is the most likely diagnosis?

Answer 21

Pheochromocytoma
Explanation
Pheochromocytoma is a catecholamine-secreting tumor that originates from the chromaffin cells (usually in the adrenal medulla). Children make up ~ 10% of cases, with most occurring between 6 and 14 years of age. These patients can have sustained or paroxysmal HTN. (In fact, anytime paroxysmal HTN occurs, pheochromocytoma is the most likely etiology.) Headache, palpitations, dizziness, sweating, emesis, and seizures are also symptoms. They have a good appetite but will have growth failure.

Question 22

Which hypothalamic hormone is responsible for the onset and progression of puberty?

Answer 22

Gonadotropin-releasing hormone (GnRH)
Explanation
Hypothalamic pulsatile GnRH secretion regulates the production of LH and FSH and thus is responsible for the onset and progression of puberty.

Question 23

A girl presents with the following:

Short stature
Webbing of the neck
Pectus carinatum
Cubitus valgus
Hypertelorism
Downward-slanting palpebral fissures
High-frequency hearing loss
Pulmonary valve stenosis
What is the most likely diagnosis?

Answer 23

Noonan syndrome
Explanation
Be careful with associations. Many see “webbing of the neck” and go for Turner syndrome because this is a girl. However, Noonan syndrome can have many of the features of Turner syndrome—a key difference here is the pulmonary stenosis. (Turner has aortic valve problems.) Intellectual disability also occurs in Noonan’s (about 25% of patients) and not Turner’s. (Although patients with Turner syndrome can have difficulty in math and problem solving.) Noonan syndrome has normal karyotype

Question 24

A newborn girl presents with the following:

Marked edema of the dorsa of her hands and feet
Loose skin folds at the nape of her neck
She is at the 5th percentile for height and weight.
What is the most likely diagnosis?

Answer 24

Turner syndrome
Explanation
This is a tough one because there isn’t much to go on. Newborns with Turner’s commonly do not have many of the typical characteristics except for the puffy hands and feet (sometimes the only clue). But the neck finding is included here! Later, the other findings appear

Question 25

A child with Type 1 diabetes mellitus (DM) presents with hyperglycemia and urine ketones.

What remaining factor establishes diabetic ketoacidosis (DKA)?

Answer 25

Acidemia in the setting of absolute insulin deficiency
Explanation
The basis of DKA is absolute insulin deficiency coupled with the pathophysiologic increases in the counter-regulatory hormone glucagon

Question 26

What is the most frequent X chromosome abnormality in girls?

Answer 26

Answer
Triple X syndrome (a.k.a. trisomy X or 47,XXX)
Explanation
Triple X syndrome occurs in 1/1,000 live-born females and is due to maternal meiotic nondisjunction. Phenotypically, girls with this disorder are normal females and not recognized routinely in infancy. By 2 years of age, however, speech and language delays manifest, along with poor coordination, poor academic performance, and immature behavior. These girls tend to be tall and gangly, commonly with behavior disorders.

Question 27

An infant is born with fetal overgrowth and hypertrophy. He has macroglossia, hepatosplenomegaly, nephromegaly, and pancreatic β-cell hyperplasia.

What is the most likely diagnosis?

Answer 27

Beckwith-Wiedemann syndrome (BWS)
Explanation
BWS is very rare, occurring in 1/14,000 births. These children are at risk for Wilms tumor, adrenocortical carcinoma, and hepatoblastoma. Hence, they need an abdominal ultrasound and α-fetoprotein frequently until age 4 years and then renal ultrasound frequently from 4 to 7 years of age. BWS has been mapped to chromosome 11p15.5.

Question 28

Patients with cleft lip or cleft palate have a 4% chance of having which endocrine deficiency?

Answer 28

Growth hormone deficiency
Explanation
A number of congenital defects can occur with regard to the pituitary. Congenital hypopituitarism generally includes growth hormone deficiency along with 1 or more of the other 5 hormones produced in the anterior pituitary. Many different congenital defects can present with hypopituitarism. The common midfacial ones are cleft lip or cleft palate and solitary maxillary central incisor

Question 29

A newborn fails his newborn screen with a low total T4. On repeat testing, he has a normal free T4 and a normal TSH.

What is the most likely diagnosis?

Answer 29

Thyroxine-binding globulin (TBG) deficiency
Explanation
TBG deficiency causes a falsely low total T4 but has a normal FT4 and a normal TSH. These children are euthyroid and therefore do not require levothyroxine replacement or further follow-up

Question 30

A 16-year-old girl has the following:

Type 1 diabetes mellitus (DM)
Autoimmune thyroiditis
Adrenal cortical insufficiency
What is the syndrome called?

Answer 30

Autoimmune polyglandular syndrome (APS) Type 2 (a.k.a. Schmidt syndrome)
Explanation
APS Type 2 is primarily Type 1 DM, thyroid disease, and/or primary adrenal insufficiency (a.k.a. Addison disease). It is associated with HLA-DR3 and HLA-DR4 and is more common in females. Remember that APS Type 2 is not a multiple endocrine neoplasia syndrome!

Question 31

A 12-year-old girl presents with:

Constipation
Weight for age that is proportionately much greater than height for age
Delayed bone age
Slow deep tendon reflexes, with a delayed relaxation phase
High TSH
Low free T4
What is the most likely diagnosis

Answer 31

Acquired hypothyroidism
Explanation
Acquired hypothyroidism is more common than congenital and is more frequently seen in girls than in boys. Its onset is typically insidious, and the most common cause is autoimmune thyroiditis. You know this is the primary disease because FT4 is low and the pituitary is trying to stimulate it to no avail with TSH, which is high.

Question 32

46,XY
Nephropathy, with renal failure common by 3 years of age
Ambiguous genitalia
Total deficiency of testicular function
What is the syndrome with these characteristics?

Answer 32

Denys-Drash syndrome
Explanation
Denys-Drash syndrome is a difference of sexual development (DSD) that occurs in 46,XY individuals and presents as described. Wilms tumor can occur as well. The total deficiency of testicular function is so complete that Müllerian ducts are found.

Question 33

A child presents with hypertension and hypokalemia. Renin is low, but aldosterone is also low. There are several family members with this syndrome.

What is the likely syndrome?

Answer 33

Liddle syndrome
Explanation
Liddle syndrome is an autosomal dominant disorder that presents as described. The problem is dysregulation of the epithelial sodium channel (ENaC), leading to a high number of the channels being in the collecting duct, leading to a clinical picture that looks like hyperaldosteronism but with a distinct etiology.

Question 34

What are screening tests for Cushing syndrome?

Answer 34

24-hour urinary free cortisol, midnight salivary cortisol, and dexamethasone suppression test
Explanation
24-hour urinary free cortisol and midnight salivary cortisol are elevated in Cushing syndrome. A low-dose dexamethasone suppression test involves giving dexamethasone 1 mg at 11 p.m. and drawing a plasma cortisol level the following morning at 8 a.m. A level > 1.8 µg/dL confirms Cushing syndrome

Question 35

A neonate presents with severe dehydration after a preterm complication of polyhydramnios. You find the infant has hyperaldosteronism with increased renin secretion without hypertension. There is also increased calcium excretion in the urine.

What is the most likely diagnosis

Answer 35

Bartter syndrome
Explanation
Bartter syndrome is a form of hyperaldosteronism with increased renin secretion but without hypertension. These patients are also at risk for kidney stones due to hypercalciuria

Question 36

A tall 16-year-old boy with mild intellectual disability presents with gynecomastia. He has normal pubic hair development, but his penis and testes are small for his age.

What is the most likely diagnosis?

Answer 36

47,XXY (Klinefelter syndrome)
Explanation
47,XXY is generally not diagnosed until puberty, when penis and testes size do not develop normally. Intellectual disability and psychiatric problems occur early. The adrenal gland is not affected, so you still see normal pubic hair development; however, the testes do not fully develop due to seminiferous tubule dysgenesis

Question 37

A newborn girl presents with virilization, no salt wasting, and hypertension.

What is the most likely diagnosis?

Answer 37

Answer
11-β-hydroxylase deficiency
Explanation
11-β-hydroxylase deficiency can be differentiated from 21-hydroxylase deficiency by the absence of salt wasting and presence of hypertension. The hypertension is due to elevation of 11-deoxycorticosterone (DOC), a potent mineralocorticoid.

Question 38

You find a solitary thyroid nodule in a 10-year-old girl.

What is the best management here, reassurance or getting tissue?

Answer 38

Get tissue
Explanation
A solitary nodule of the thyroid is much more likely to be cancerous in children than adults; therefore, reassurance in this case is insufficient! According to the 2015 American Thyroid Association evaluation guidelines, do the following when there is suspicion of a nodule:

1) Obtain thyroid U/S to evaluate for size and features of the nodule.
2) Check TSH; if TSH is suppressed, do thyroid uptake scan to evaluate for a hot nodule. Hyperfunctioning nodules require surgical removal to treat hyperthyroidism.
3) If a nodule is present and not hyperfunctioning, do fine needle aspiration (FNA) under U/S guidance.
4) If the FNA is:
• benign, repeat U/S in 6–12 months; inadequate or nondiagnostic, repeat U/S and FNA in 3–6 months;
• indeterminate or suspicious, perform surgery.

Question 39

Which gene on the Y chromosome is necessary for male phenotype to occur?

Answer 39

Answer
The SRY gene
Explanation
Ordinarily, male traits require a Y chromosome and specifically, an intact SRY gene and other genes to direct the undifferentiated gonad into a testis. Conditions exist wherein an X chromosome atypically has an intact SRY gene, resulting in an XX male phenotype, or a Y chromosome loses its SRY gene, resulting in an XY female phenotype

Question 40

A newborn presents with the following findings:

Absence of the optic chiasm
Optic nerve hypoplasia
Agenesis of the corpus callosum
Hypothalamic insufficiency
What is the likely syndrome?

Answer 40

Septooptic dysplasia (SOD)
Explanation
SOD commonly involves the hypothalamic-pituitary axis and can affect the anterior, posterior, or both axes. It is associated with an abnormality in the transcription factor HESX1.

Question 41

A short child presents with the following:

Normal growth velocity
Normal bone age
Family history of short stature
What is the most likely diagnosis?

Answer 41

Genetic short stature
Explanation
The 3 etiologies of short stature are constitutional growth delay, genetic short stature, and growth hormone deficiency. Use growth velocity, bone age, and family history to differentiate among these. Of the 3, only genetic short stature presents with normal bone age.

Question 42

A 15-year-old girl presents with the following:

Low posterior hairline
Small mandible
Prominent ears
Epicanthal folds
Broad chest with widely spaced nipples
Cubitus valgus
“Spooning” of her fingernails
Short stature
Sensorineural hearing loss
Sexual maturity rating (SMR; a.k.a. Tanner) 1–2 breast development; pubic hair, axillary hair are SMR 4
Primary amenorrhea
What is the most likely cardiac abnormality in this patient?

Answer 42

Nonstenoic bicuspid aortic valve
Explanation
The girl has Turner syndrome (45,X). Be aware that the only 100%, always-present finding for Turner syndrome is the short stature. The rest of the listed findings in this question may or may not be there. (We even left out the classic webbed neck.) Bicuspid aortic valve occurs in nearly 50% of girls with Turner syndrome, and 20% have aortic coarctation. Due to their risk of aortic dissection, follow up with cardiology and get an echocardiogram every 5–10 years for life

Question 43

A child is born to a woman at home. The mother is distrustful of modern health care and does not seek medical attention for herself or her baby after delivery. The baby is brought in by the child’s grandmother who has temporary custody of the child because her daughter has schizophrenia and has been admitted to a psychiatric hospital. The child is listless and somnolent. Her temperature is 94.5°F (34.7°C), and she has an open posterior fontanelle.

What is the most likely diagnosis

Answer 43

Congenital hypothyroidism
Explanation
An open posterior fontanelle is the most classic finding for congenital hypothyroidism in the newborn. Another common finding is a lack of the distal femoral epiphysis. This is normally present at birth but is absent in hypothyroid infants. Without therapy, affected infants progress to global developmental delay with significantly poor linear growth. Early detection is clinically difficult, leading to universal newborn screening of all infants. Prognosis is good for those who begin treatment in the first few weeks of life.

Question 44

What is the most common cause of congenital hypothyroidism

Answer 44

Answer
Thyroid dysgenesis
Explanation
Thyroid dysgenesis (including dysgenesis, agenesis, and ectopic thyroid) is the most common cause of congenital hypothyroidism, resulting in > 90% of the diagnoses. Congenital hypothyroidism occurs in 1/2,000–4,000 newborns

Question 45

What drug is most commonly known to induce nephrogenic diabetes insipidus (DI)?

Answer 45

Answer
Lithium
Explanation
Disorders associated with nephrogenic DI include polycystic kidney disorder, sickle cell disease, chronic pyelonephritis, sarcoidosis, amyloidosis, and urinary tract obstruction

Question 46

A child is born with normal stature and complete female phenotype at birth with vagina, uterus, and fallopian tubes. However, she does not develop breasts or menstruate at puberty. The gonads are undifferentiated streaks. Chromosome analysis is performed, and she is XY.

What is the name of this syndrome

Answer 46

Swyer syndrome (a.k.a. XY pure gonadal dysgenesis)
Explanation
An individual with Swyer syndrome has karyotype 46,XY and is phenotypically female at birth due to pure gonadal dysgenesis. Dysgenesis results in an absence of Leydig cells, so there is no testosterone to support the Wolffian structures. Also, the Sertoli cells do not form, so the Müllerian structures develop. Most cases are due to a mutation in the SRY gene, but the Y chromosome is cytogenetically normal.

Question 47

A pregnant woman is exposed to androgens after the 13th week of gestation.

What is the likely effect on her developing daughter?

Answer 47

Clitoral enlargement
Explanation
Congenital adrenal hyperplasia (CAH) in the mom or the baby is the most common cause of 46,XX DSD. If the adrenal exposure was during weeks 8−13, the baby can have labial fusion. Continual androgen exposure from 8 weeks of gestation to birth causes clitoral enlargement and labial fusion

Question 48

A tumor has destroyed the pituitary stalk, and the patient has developed pituitary hormone deficiency.

What tumor is most likely to do this?

Answer 48

Craniopharyngioma
Explanation
Due to its precarious location in the intrasellar space, craniopharyngioma is the most common tumor to destroy the hypothalamus, pituitary, or its stalk and cause pituitary hormone deficiency. Radiation or previous surgery also can cause problems.

Question 49

What is the most common brain lesion to cause central precocious puberty (CPP)?

Answer 49

Hypothalamic hamartoma
Explanation
Hypothalamic hamartoma consists of ectopic neural tissue that contains GnRH-secretory neurons and functions as an accessory GnRH pulse generator. On MRI, it appears as a small, pedunculated mass attached to the tuber cinereum or on the floor of the 3rd ventricle. Other lesions causing CPP include postencephalitic scars, tuberculous brain involvement, hydrocephalus, tuberous sclerosis, head trauma, and neoplasms (about 50% are germinomas or astrocytomas

Question 50

A child with Type 1 diabetes mellitus presents with high morning blood glucose levels. You draw a 3 a.m. glucose, and it is 95 mg/dL, but the 7 a.m. glucose is 210 mg/dL.

What is the likely diagnosis?

Answer 50

Dawn phenomenon
Explanation
The dawn phenomenon is due to the waning effects of available insulin due to increased clearance of insulin and to nocturnal increases in GH and other counter-regulatory hormones, which antagonizes insulin’s metabolic effects.

Question 51

A child with Type 1 diabetes mellitus (DM) is diagnosed with influenza.

Will this child’s insulin requirement increase or decrease?

Answer 51

Increase
Explanation
During intercurrent illnesses, whether infection or trauma, children with diabetes require more insulin than their baseline. A good rule is to add 10–20% to each dose of the rapid-acting insulin given for meal coverage or glucose correction. Subsequent increases or decreases can be based on successive blood sugar and ketone monitoring.

Question 52

A 6-year-old boy had a severe motor vehicle accident with resulting fractures that required him to be immobilized in bed for 6 months. At about 4 months into his immobilization, he presents with:

Nausea
Emesis
Increased bed wetting
Which electrolyte abnormality is most likely

Answer 52

Hypercalcemia
Explanation
Immobilization results in stimulation of bone resorption, increasing the risk of hypercalcemia. Because immobilization hypercalcemia is a less common cause of hypercalcemia, testing must be done to rule out other more common causes, such as hyperparathyroidism (the most common cause). Laboratory testing for this condition shows elevated serum calcium of > 12 mg/dL, and suppressed parathyroid hormone (PTH) levels.

Question 53

A 5-year-old girl has a solitary maxillary central incisor.

Which endocrine deficiency is likely?

Answer 53

Growth hormone deficiency
Explanation
Midfacial anomalies, such as a solitary maxillary central incisor, indicate a high likelihood of growth hormone deficiency

Question 54

What is the management of a child newly diagnosed with Type 2 diabetes mellitus (DM) who presents with ketosis or diabetic ketoacidosis (DKA)?

Answer 54

Insulin, diet, and exercise
Explanation
Start children with Type 2 DM who are metabolically decompensated at the time of presentation on IV fluids and insulin drip as the 1st line treatment. Weight loss through lifestyle changes is included in daily therapy. This treatment can be continued until the child is metabolically stable; then the child can be weaned off insulin if possible.

Question 55

An adolescent girl who takes no medication except for oral contraceptive pills (OCPs) presents with abnormal laboratory tests. She had been “tired,” so someone had ordered a total T4, which came back elevated. Repeat testing shows a normal FT4 and a normal TSH.

What is causing the total T4 to be elevated?

Answer 55

Oral contraceptive pills
Explanation
OCPs are increasing her estrogen levels, which increases her thyroxine-binding globulin (TBG), resulting in an elevated total T4 but still a normal FT4. Because she is euthyroid, her TSH is normal as well.

Question 56

Intrauterine growth restriction
Fasting hypoglycemia
Postprandial hyperglycemia with profound insulin resistance
Serum insulin levels are 100× normal.
Acanthosis nigricans
Death is common before 1 year of age.
What is the syndrome with these characteristics?

Answer 56

Donohue syndrome (a.k.a. leprechaunism)
Explanation
Donohue syndrome is a rare syndrome with the listed characteristics. The profound insulin resistance is usually caused by mutation or deletion of both insulin receptor genes.

Question 57

What urine test should be done to detect signs of kidney disease in patients with diabetes?

Answer 57

Urine microalbumin
Explanation
The American Diabetes Association (ADA) screening guidelines recommend annual urine albumin excretion testing, starting 5 years after diagnosis. Per the ADA guidelines, treat patients who have ­persistent micro- or macroalbuminuria with angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs)

Question 58

A 4-year-old girl presents with vaginal bleeding. You note that she has very large café au lait spots, and bone radiographs show fibrous dysplasia of the skeletal system.

What is the most likely diagnosis?

Answer 58

McCune-Albright syndrome (MAS)
Explanation
In girls, MAS presents with early vaginal bleeding (the classic endocrine presentation for this syndrome). These girls have markedly enlarged ovaries and cysts. There is evidence of autonomous endocrine hyperfunction due to a missense mutation in the alpha subunit of the stimulatory G protein. The glands work independently, and there is no feedback loop. Clinically, you can see activation of all G-protein–coupled receptors: TSH, FSH, LH, GHRH, and ACTH receptors.

Question 59

A child presents with:

Retinitis pigmentosa
Obesity
Intellectual disability
Polydactyly
Genital hypoplasia with hypogonadism
What syndromes present with these findings?

Answer 59

Laurence-Moon and Bardet-Biedl syndromes
Explanation
With regard to these syndromes, remember the retinitis pigmentosa with hypogonadism.

Question 60

A 17-year-old girl presents with:

Increased pigmentation of her hands and face, particularly in the creases of her palms
Increased pigmentation is also especially prominent around her umbilicus, axilla, and nipples.
Anorexia
Fatigue
Nausea and vomiting without diarrhea
Salt craving
Weakness
What is the most likely diagnosis?

Answer 60

Answer
Primary adrenal insufficiency (a.k.a. Addison disease)
Explanation
Primary adrenal insufficiency (a.k.a. Addison disease) is the most common etiology of adrenal insufficiency and is predominantly caused by autoimmune destruction of the adrenal cortex, with antiadrenal antibodies detected in the plasma. The diagnostic key here is the increased pigmentation, which is due to excess proopiomelanocortin (POMC), a precursor polypeptide for ACTH and melanocyte-stimulating hormone (MSH). In adrenal insufficiency, the low cortisol causes an increase in POMC, and having increased ACTH and MSH results in hyperpigmentation. Salt craving is also a classic finding.