USMLE Step 1 Quiz
Practice Metabolic And Growth Disorders in USMLE Step 1 with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.
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An 18-year-old individual is evaluated for primary amenorrhea. Physical examination reveals a tall, phenotypically female patient with well-developed breasts but absent axillary and pubic hair. Pelvic examination shows a blind-ending vaginal pouch. Karyotype analysis reveals 46,XY. Further investigation confirms the presence of intra-abdominal testes.
A defect in which of the following is the underlying cause of this patient's condition?
This quiz focuses on Metabolic And Growth Disorders, giving you a quick way to practice the rules, question types, and explanations that matter most for USMLE Step 1.
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An 18-year-old individual is evaluated for primary amenorrhea. Physical examination reveals a tall, phenotypically female patient with well-developed breasts but absent axillary and pubic hair. Pelvic examination shows a blind-ending vaginal pouch. Karyotype analysis reveals 46,XY. Further investigation confirms the presence of intra-abdominal testes.
A defect in which of the following is the underlying cause of this patient's condition?
Explanation: This is a classic presentation of complete androgen insensitivity syndrome (CAIS). The patient is genetically male (46,XY) and has functional testes that produce testosterone and Müllerian inhibitory factor (MIF). However, a defect in the androgen receptor prevents target tissues from responding to androgens. The presence of MIF causes regression of Müllerian structures (no uterus, fallopian tubes). The testosterone is aromatized to estrogen, leading to breast development. The lack of androgen effect explains the female external genitalia and absence of pubic/axillary hair.
A 16-year-old patient with a 46,XY karyotype presents with primary amenorrhea and a female phenotype. She has normal breast development (Tanner stage 4) but scant pubic and axillary hair. Testes are palpable in the labia majora. Serum testosterone levels are in the high-normal range for an adult male.
The development of female external genitalia in this patient is due to the failure of which of the following embryological processes?
Explanation: This patient has androgen insensitivity syndrome (AIS). The 46,XY karyotype and presence of testes indicate genetic maleness. The testes produce both anti-Müllerian hormone (causing Müllerian duct regression) and testosterone. However, due to defective androgen receptors, testosterone and its metabolite DHT cannot exert their effects. This leads to a failure of virilization of the urogenital sinus, genital tubercle, and labioscrotal folds, which then develop along the default female pathway, resulting in female external genitalia.
A 10-year-old boy is brought to the pediatrician for concerns about his height. He has consistently been below the 3rd percentile for height and weight since age 2. His parents are of average height. Physical examination reveals a boy with a cherubic face and mild central adiposity. His bone age is determined to be 7 years. Laboratory studies show low levels of both insulin-like growth factor 1 (IGF-1) and growth hormone (GH). A GH stimulation test fails to produce a rise in serum GH.
Dysfunction in which of the following glands is the most likely cause of this patient's condition?
Explanation: The patient's presentation of short stature, delayed bone age, low IGF-1, and a blunted response to GH stimulation testing is classic for growth hormone deficiency. Growth hormone is produced and secreted by the somatotroph cells of the anterior pituitary. Therefore, dysfunction of the anterior pituitary is the most likely cause.
A newborn in a remote village is noted to have ambiguous genitalia. The infant is phenotypically female but has clitoromegaly and posterior labial fusion. Karyotype is 46,XY. The child is raised as a girl. At age 12, she experiences deepening of the voice, growth of a phallus, and development of a male body habitus. Internal structures include testes, epididymis, and vas deferens.
This patient's clinical course is best explained by a deficiency of which of the following enzymes?
Explanation: This patient has 5-alpha-reductase deficiency, an autosomal recessive disorder affecting 46,XY individuals. This enzyme is responsible for converting testosterone to the more potent dihydrotestosterone (DHT). DHT is required for the development of the external male genitalia in utero. Its deficiency leads to ambiguous or female-like external genitalia at birth. At puberty, the surge in testosterone can induce virilization, causing phallic growth, voice deepening, and muscle development.
A 55-year-old man with a recent diagnosis of diabetes mellitus presents with a persistent, painful skin rash. The rash consists of erythematous plaques with central clearing and crusting, primarily on his perineum, buttocks, and lower extremities. He has also experienced significant unintentional weight loss and intermittent diarrhea. A CT scan of the abdomen reveals a mass in the tail of the pancreas.
This patient's condition is most likely caused by a tumor secreting which of the following hormones?
Explanation: This patient's constellation of symptoms, including diabetes mellitus, weight loss, diarrhea, and the characteristic skin rash known as necrolytic migratory erythema, is classic for glucagonoma syndrome. This is caused by a glucagon-secreting tumor of the pancreatic alpha cells. The diagnosis is confirmed by a markedly elevated serum glucagon level.
A 7-year-old girl is brought to the clinic due to profound short stature. Her height is far below the 1st percentile. She has a prominent forehead and a small mandible. Laboratory testing reveals an extremely low level of serum insulin-like growth factor 1 (IGF-1) but a markedly elevated level of serum growth hormone (GH).
A defect in which of the following is the most likely cause of this patient's condition?
Explanation: This patient presents with Laron syndrome, a form of dwarfism characterized by growth hormone insensitivity. It is caused by a defect in the growth hormone receptor. The anterior pituitary produces adequate or even excessive GH, but the target tissues (primarily the liver) cannot respond to it. This leads to a failure to produce IGF-1, resulting in short stature despite high GH levels. The lack of negative feedback from IGF-1 on the pituitary leads to the elevated GH.
A 6-year-old girl is brought to her pediatrician because her mother is concerned about her early development. The mother reports that the child developed breast buds at age 5 and started her first menstrual period 2 months ago. On examination, she is at the 95th percentile for height. Tanner stage 3 breast and pubic hair development are noted. A GnRH stimulation test is performed, which results in a significant rise in LH and FSH levels.
This patient's condition is most likely caused by which of the following mechanisms?
Explanation: This patient has central precocious puberty, also known as gonadotropin-dependent precocious puberty. The key diagnostic finding is the pubertal response (a significant rise in LH and FSH) to a GnRH stimulation test. This indicates that the hypothalamic-pituitary-gonadal (HPG) axis has been prematurely activated, leading to the early onset of puberty. It is often idiopathic in girls but can be caused by CNS lesions.
A 17-year-old boy is evaluated for failure to begin puberty. He has not experienced a growth spurt and has no facial hair. Physical examination reveals a tall, eunuchoid body habitus with long limbs. He has small, soft testes and gynecomastia. He also reports having no sense of smell. Laboratory studies show low testosterone and low LH and FSH levels.
This patient's lack of smell is most likely related to a developmental failure of which of the following?
Explanation: The combination of hypogonadotropic hypogonadism (delayed puberty with low LH and FSH) and anosmia (lack of smell) is characteristic of Kallmann syndrome. This genetic disorder results from the failed migration of GnRH-releasing neurons from their origin in the olfactory placode to their final destination in the hypothalamus during embryonic development. This leads to a deficiency of GnRH and subsequent failure to initiate puberty.
A 16-year-old boy is brought for evaluation because he has not yet started puberty. His parents note that he is much shorter than his peers. On physical examination, he has sparse pubic and axillary hair, and his testes are small for his age. Family history is notable for his father having a similar late growth spurt and development, starting at age 17. His bone age is 13 years.
What is the most likely diagnosis for this patient?
Explanation: This patient's presentation of delayed puberty, short stature for chronological age, delayed bone age, and a positive family history is classic for constitutional delay of growth and puberty. This is a common, benign variant of normal development where the tempo of growth and maturation is slower, but eventual adult height and sexual development are normal.
A 19-year-old man is evaluated for infertility. Physical examination reveals a tall, slim male with disproportionately long legs. He has gynecomastia, sparse body hair, and small, firm testes measuring 2 cm in length.
Which of the following karyotypes is most likely to be found in this patient?
Explanation: The clinical features described—tall stature with eunuchoid proportions, gynecomastia, and small, firm testes—are characteristic of Klinefelter syndrome. This genetic disorder is caused by the presence of an extra X chromosome in males, resulting in a 47,XXY karyotype. The condition leads to primary hypogonadism with testicular atrophy, low testosterone, and elevated gonadotropins (hypergonadotropic hypogonadism).
A 15-year-old girl presents with primary amenorrhea and short stature. On examination, she is at the 3rd percentile for height. She has a broad, shield-like chest with widely spaced nipples, a low posterior hairline, and a webbed neck. Pelvic ultrasound reveals bilateral streak gonads.
This patient's condition is associated with an increased risk of which of the following cardiovascular abnormalities?
Explanation: This patient's clinical presentation is classic for Turner syndrome (45,X karyotype). In addition to short stature and gonadal dysgenesis, patients with Turner syndrome have a significantly increased risk of congenital cardiovascular abnormalities. The most common are bicuspid aortic valve and coarctation of the aorta.
A 2-week-old female infant is brought to the emergency department with vomiting, poor feeding, and lethargy. Physical examination reveals ambiguous genitalia with an enlarged clitoris and fused labia. Laboratory studies show hyponatremia, hyperkalemia, and hypoglycemia. Her blood pressure is low.
A deficiency of which of the following enzymes is the most likely cause of this infant's condition?
Explanation: This infant presents with salt-wasting congenital adrenal hyperplasia (CAH), which is most commonly caused by 21-hydroxylase deficiency. This enzyme defect impairs the synthesis of both cortisol and aldosterone. The lack of aldosterone leads to salt wasting (hyponatremia, hyperkalemia) and hypotension. The lack of cortisol leads to hypoglycemia and increased ACTH secretion. The precursors proximal to the block are shunted towards androgen synthesis, causing virilization (ambiguous genitalia) in female infants.
A 32-year-old woman presents with a 6-month history of irregular menstrual periods and a milky discharge from her nipples. She and her husband have been trying to conceive for a year without success. She also complains of headaches and some peripheral vision loss. Her serum prolactin level is markedly elevated.
The most likely cause of her symptoms is a neoplasm originating from which of the following cell types?
Explanation: The patient's symptoms of galactorrhea (milky nipple discharge), amenorrhea (irregular periods), and infertility, along with a high prolactin level, are characteristic of hyperprolactinemia. The most common cause of significant hyperprolactinemia is a prolactin-secreting pituitary adenoma, also known as a prolactinoma. These tumors arise from the lactotroph cells of the anterior pituitary. The headaches and visual field defects (bitemporal hemianopsia) are due to the mass effect of the tumor on the optic chiasm.
A 9-year-old boy presents with progressive headaches, nausea, and difficulty seeing the blackboard at school. An ophthalmologic exam reveals bitemporal hemianopsia. An MRI of the brain shows a suprasellar, partially cystic mass with calcifications. The patient's growth chart shows a recent deceleration in height velocity.
This patient's tumor is most likely derived from which of the following embryologic structures?
Explanation: The clinical and radiological findings—a child with a suprasellar calcified mass causing visual field defects and endocrine dysfunction (growth failure)—are classic for a craniopharyngioma. These benign but locally invasive tumors are derived from remnants of Rathke's pouch, the embryologic precursor of the anterior pituitary gland.
A 44-year-old man is diagnosed with a gastrin-secreting tumor of the pancreas. He has a history of recurrent kidney stones and was recently found to have an elevated serum calcium level. His mother and sister both had parathyroid surgery at a young age. Further workup with a brain MRI is considered.
This patient's constellation of findings is most consistent with which of the following syndromes?
Explanation: This patient has multiple endocrine neoplasia, type 1 (MEN1), an autosomal dominant disorder characterized by the '3 Ps': Parathyroid tumors (hyperparathyroidism, causing hypercalcemia and kidney stones), Pancreatic endocrine tumors (e.g., gastrinoma causing Zollinger-Ellison syndrome), and Pituitary adenomas. The patient's gastrinoma and hyperparathyroidism, along with a positive family history, strongly suggest MEN1.
A 35-year-old woman undergoes a total thyroidectomy for a nodule that was diagnosed as medullary thyroid carcinoma on fine-needle aspiration. Her past medical history is significant for episodes of paroxysmal hypertension, palpitations, and headaches. Laboratory evaluation reveals elevated urinary metanephrines. Her serum calcium is also mildly elevated.
This patient should be screened for a mutation in which of the following genes?
Explanation: The patient's triad of medullary thyroid carcinoma (MTC), pheochromocytoma (suggested by paroxysmal hypertension and elevated metanephrines), and primary hyperparathyroidism (suggested by elevated calcium) is characteristic of multiple endocrine neoplasia, type 2A (MEN2A). MEN2A and MEN2B are caused by germline activating mutations in the RET proto-oncogene.
A 22-year-old man presents for evaluation of a thyroid nodule. He is noted to be very tall and thin with long arms and fingers. Physical examination reveals multiple small, flesh-colored nodules on his lips and tongue. A biopsy of the thyroid nodule confirms medullary thyroid carcinoma. His 24-hour urine collection shows elevated catecholamine metabolites.
In addition to medullary thyroid carcinoma and pheochromocytoma, which of the following is a characteristic feature of this patient's syndrome?
Explanation: This patient's presentation with medullary thyroid carcinoma, pheochromocytoma, marfanoid habitus (tall, thin), and nodules on the lips and tongue is classic for multiple endocrine neoplasia, type 2B (MEN2B). The characteristic features that distinguish MEN2B from MEN2A are the presence of mucosal neuromas (on lips, tongue, conjunctivae), marfanoid body habitus, and the absence of hyperparathyroidism.
A 48-year-old woman presents with episodes of confusion, diaphoresis, and palpitations that occur in the late morning if she skips breakfast. These symptoms are relieved by eating. During one such episode in the clinic, her fingerstick glucose is 42 mg/dL. A supervised 72-hour fast is initiated. On day 2, she develops symptoms, and simultaneous blood tests are drawn.
Which of the following sets of laboratory findings would be most consistent with an insulinoma?
Explanation: The diagnosis of an insulinoma, a tumor of pancreatic beta cells, is confirmed by documenting Whipple's triad (symptoms of hypoglycemia, low plasma glucose, and relief of symptoms with glucose administration) along with inappropriately high insulin levels. During hypoglycemia, normal beta cells would be suppressed. An insulinoma autonomously secretes insulin, leading to high insulin levels despite low glucose. Because the insulin is endogenous, C-peptide (which is cleaved from proinsulin during insulin synthesis) will also be elevated. Exogenous insulin administration would cause high insulin but low C-peptide.
A 60-year-old woman presents with mild diabetes mellitus, steatorrhea, and abdominal pain. An abdominal ultrasound performed for the pain reveals gallstones. Laboratory studies show mild hyperglycemia. A CT scan of the abdomen identifies a mass in the head of the pancreas.
A tumor secreting an excess of which of the following hormones best explains this triad of symptoms?
Explanation: The classic triad for a somatostatinoma is diabetes mellitus (due to inhibition of insulin and glucagon secretion), steatorrhea (due to inhibition of pancreatic exocrine secretions and cholecystokinin), and cholelithiasis (due to inhibition of gallbladder motility). Somatostatin is a potent inhibitor of many gastrointestinal and pancreatic hormones, leading to this constellation of findings.
A 45-year-old man presents with a 1-year history of severe, recurrent epigastric pain that is partially relieved by antacids. He has been treated for multiple duodenal ulcers, but they continue to recur despite standard proton pump inhibitor therapy. He also complains of chronic diarrhea and heartburn. An upper endoscopy reveals multiple, large ulcers in the duodenum and jejunum.
Overproduction of which hormone is the most likely cause of this patient's condition?
Explanation: The presentation of multiple, refractory peptic ulcers, especially in atypical locations like the jejunum, is highly suggestive of Zollinger-Ellison syndrome (ZES). ZES is caused by a gastrin-secreting tumor (gastrinoma), most commonly located in the pancreas or duodenum. The excessive gastrin stimulates parietal cells to secrete massive amounts of gastric acid, leading to severe peptic ulcer disease and inactivation of pancreatic enzymes (causing diarrhea/steatorrhea).