A 2-month-old boy is brought to the emergency department due to progressively worsening “floppiness” and poor feeding.  The infant was born in Eastern Europe via an uncomplicated vaginal delivery to a 38-year-old woman and then immigrated to the United States with his family.  The parents describe the infant as a “good baby” who rarely cries and sleeps through the night but has lately been difficult to rouse for breastfeeding.  Stools have also decreased to every other day and are small and pellet-like.  Physical examination shows a hypotonic infant with a large anterior fontanelle, large tongue, and a reducible umbilical hernia.  He has low tone and is unable to hold his head erect on his own.  No other abnormalities are seen.  Which of the following is the most likely cause of this patient’s condition?

A 34-year-old woman comes to the office due to a 1 week history of mood swings, difficulty concentrating, and hand tremors.  She also has pain at the front of her neck that radiates to her ears and is worse with swallowing.  The patient initially attributed her symptoms to a flu-like illness that she had a few weeks earlier.  She has no other medical conditions and takes no medications.  Blood pressure is 140/80 mm Hg and pulse is 105/min.  The thyroid gland is very tender on palpation.  After initial laboratory testing, a thyroid scan is performed and reveals diffusely decreased radioiodine uptake.  Erythrocyte sedimentation rate is 105 mm/hr.  Which of the following pathological changes would be most likely on biopsy of this patient’s thyroid gland?

A 61-year-old woman comes to the office due to a neck lump.  She is otherwise in good health and has no other symptoms.  Temperature is 36.7 C (98.1 F), blood pressure is 115/70 mm Hg, and pulse is 78/min.  On physical examination, there is a nontender, firm nodule in the left lobe of the thyroid.  Laboratory results show a normal serum TSH level.  Thyroid ultrasonography reveals a 2-cm, hypoechoic thyroid nodule with increased central blood flow.  Fine-needle aspiration biopsy shows clusters of cells with large, overlapping nuclei containing finely dispersed chromatin.  Numerous intranuclear inclusion bodies and grooves are also seen.  Which of the following is the most likely diagnosis?

A 55-year-old man comes to the office to establish care after relocating to the area.  The patient has a 6-year history of type 2 diabetes mellitus for which he takes metformin monotherapy.  He feels well and has no other medical conditions.  The patient does not use tobacco or alcohol.  He consumes a balanced diet and jogs for 40 minutes every morning.  Review of his blood glucose journal over the last few months shows fasting glucose levels of 150-180 mg/dL.  Laboratory analysis shows a hemoglobin A1c level of 4%.  Further evaluation with hemoglobin electrophoresis shows a hemoglobin A2 level of 7.5% (normal: 1.5%-3.5%).  Which of the following is the most likely explanation for this patient’s lower-than-expected hemoglobin A1c level?

A 51-year-old woman comes to the office due to progressively worsening fatigue, weight gain, and constipation for the past 6 months.  The patient has had difficulty performing daily activities due to her fatigue.  She has no significant medical history and takes no medications.  The patient has no drug allergies and does not use tobacco, alcohol, or illicit drugs.  Blood pressure is 110/80 mm Hg and pulse is 55/min.  Physical examination shows mild, diffuse enlargement of the thyroid gland.  Cardiopulmonary and abdominal examinations are normal.  Biopsy of this patient’s thyroid is most likely to show which of the following findings?

A 54-year-old man comes to the office due to worsening fatigue, generalized weakness, and an unintentional 7-kg (15.4-lb) weight loss over the past several weeks.  The patient has no prior medical conditions and takes no medications.  He has a 40-pack-year history of smoking and does not use alcohol or illicit drugs.  Blood pressure is 160/100 mm Hg and pulse is 80/min.  Physical examination shows darkening of the skin in sun-exposed areas.  There are scattered ecchymoses on the extremities.  Mild proximal muscle weakness is present.  Chest imaging reveals a 6-cm, irregular right lung mass with mediastinal lymphadenopathy.  Which of the following is most likely responsible for the patient’s current symptoms?

A 4-year-old boy is brought to the clinic after his mother noticed he was developing pubic hair.  The boy had a recent growth spurt and is now taller than his 5-year-old brother.  The patient’s preschool teacher recently mentioned he has body odor after he runs or plays.  Height is at the 95th percentile for age, and weight is at the 80th percentile.  Examination reveals sparse growth of long, pigmented hair at the base of the penis and in both axillae.  Testes are present bilaterally and appear normal.  Laboratory assessment reveals high serum concentrations of 17-hydroxyprogesterone and testosterone.

Item 1 of 2

Which of the following is most likely present in this patient?

Item 2 of 2

After initial assessment, the appropriate interventions are initiated.  Targeted suppression of which of the following hormones is the best next step to limit androgen overproduction?

53-year-old woman comes to the physician for a routine check-up.  She has no current complaints.  Her past medical history is significant for osteoarthritis of the right knee.  Her mother suffered from hypertension and was diagnosed with breast cancer at age 68, from which she died 4 years later.  Her father had diabetes mellitus and died in a motor vehicle accident at age 56.  The patient’s blood pressure is 140/85 mm Hg and heart rate is 80/min.  Physical examination is normal.  Laboratory testing is significant for a fasting blood glucose level of 140 mg/dL on more than 2 occasions.  This patient is most likely to die from which of the following conditions?

A 50-year-old man is brought to the emergency department due to a sudden, severe headache associated with nausea and vomiting that started earlier in the day.  The patient has had mild headaches and decreased libido over the past 3 months.  He has no other medical conditions and takes no medications.  Physical examination reveals bilateral visual field deficits and impaired extraocular eye movements on the right side.  Shortly after being admitted to the hospital, he becomes acutely hypotensive and loses consciousness.  The patient dies despite aggressive resuscitation efforts.  Which of the following is most likely to be found on autopsy?

A 45-year-old previously healthy man comes to the office for evaluation of a neck lump.  The patient first noticed the swelling a month ago while shaving, and it has progressively enlarged.  He has had no fever, neck pain, hoarseness, or difficulty breathing or swallowing.  The patient does not use tobacco, alcohol, or illicit drugs.  Temperature is 36.7 C (98 F), blood pressure is 110/70 mm Hg, and pulse is 78/min.  On physical examination, there is a nontender, firm nodule in the upper portion of the left thyroid lobe.  Laboratory studies reveal a normal serum TSH and elevated serum calcitonin levels.  Neck ultrasonography shows a 2-cm hypoechoic thyroid nodule with microcalcifications.  Fine-needle aspiration of the nodule reveals spindle-shaped cells in an amorphous background.  Which of the following gene alterations most likely contributed to this patient’s current condition?

A 60-year-old woman comes to the office due to difficulty climbing stairs and dyspnea on exertion over the last 6 weeks.  The patient has a 40-pack-year smoking history.  Blood pressure is 160/90 mm Hg and pulse is 78/min.  Auscultation of the chest reveals decreased breath sounds over the right lung base.  Proximal muscle strength is 4 on a scale of 0-5.  Skin examination shows scattered ecchymoses.  Laboratory results show mild hyperglycemia and elevated 24-hour urinary free cortisol.  Serum cortisol level is at the upper limit of normal and is not suppressed following administration of low-dose dexamethasone.  Serum ACTH level is elevated.  Chest x-ray reveals a right lower lobe lung mass.  Which of the following changes are most likely to occur after administration of high-dose dexamethasone in this patient?

A 3-year-old boy is brought to the emergency department due to high fever, vomiting, and lethargy.  His symptoms started 1 day ago but rapidly worsened over the last few hours.  Physical examination shows hypotension, tachycardia, neck stiffness, and a petechial rash over the trunk and lower extremities.  Laboratory results are as follows:

While being evaluated, the patient develops apnea and asystole.  Despite aggressive resuscitation efforts, the patient dies.  Autopsy would most likely reveal which of the following?

A 24-year-old woman, gravida 1 para 1, comes to the office for postpartum follow-up 2 weeks after a term vaginal delivery.  Her baby is doing well, but she is concerned because she has not yet lactated.  The patient knew she would lose weight and be tired after the baby was born, but she feels excessive fatigue and has had significant weight loss.  She also has nausea, loss of appetite, and postural dizziness.  The patient has no headaches, visual problems, cold intolerance, constipation, or polyuria.  On examination, she appears fatigued and has mild pallor.  Laboratory tests are drawn the next morning at 8:00 AM, with the following results:

Which of the following pathologic processes is most likely responsible for this patient’s symptoms?

A 30-year-old man comes to the office with a neck lump.  The patient is otherwise asymptomatic and discovered the nodule incidentally while showering.  His medical history is significant for a recently diagnosed pheochromocytoma, which was successfully removed.  The patient’s father died of thyroid cancer in his 30s.  An ultrasound reveals a hypoechoic 3-cm nodule in the right lobe of the thyroid gland.  Fine-needle biopsy of the nodule is consistent with a subtype of thyroid cancer.  The patient undergoes total thyroidectomy with central neck dissection.  Which of the following is the most likely histological finding?

A 14-year-old boy is brought to the office due to painless nodules on his lips and tongue.  The lesions appeared several months ago and have been progressively enlarging.  The patient underwent total thyroidectomy 5 years ago following the discovery of a thyroid mass and takes replacement thyroid hormone.  On physical examination, the patient is tall and slender with disproportionately long arms and legs.  His fingers are also long and thin, and joint laxity is present.  Eye examination is normal and oral inspection reveals several small, soft, flesh-colored papules on his lips and tongue.  Serum TSH is within normal limits.  This patient most likely has which of the following conditions?

A 27-year-old woman comes to the office for evaluation of infertility.  The patient and her husband have been trying to conceive for the past 2 years but have been unsuccessful.  Her husband recently underwent infertility evaluation and was found to have no abnormalities.  The patient’s menses began at age 13, and her menstrual cycles were regular until the last few years, when they began occurring at intervals of 3-4 months.  She has occasional headaches but no other symptoms.  The patient has no prior medical conditions and takes no medications.  On physical examination, the patient appears normal and has well-developed secondary sexual characteristics.  Cardiopulmonary and abdominal examinations are normal.  Pelvic examination reveals no adnexal masses.  Neurological examination shows diminished vision in the bilateral temporal visual fields.  Examination of the other cranial nerves is normal and there is no focal weakness or sensory loss.  An abnormality originating in which of the following is the most likely cause of this patient’s current condition?

A 46-year-old woman comes to the office with a painful rash involving her groin and legs that has been worsening over the last 2 weeks.  She was diagnosed with diabetes mellitus 6 months ago but has no other medical problems other than occasional loose stools.  Physical examination shows coalescing erythematous plaques with crusting and scaling at the borders and central areas of brownish induration.  Biopsy of the lesions reveals superficial necrolysis.  Which of the following laboratory abnormalities is most likely to be present in this patient?

A 43-year-old woman comes to the office due to episodic confusion, blurred vision, tremors, and sweating.  The episodes have increased in intensity in the past few months and seem to occur any time during the day.  Her symptoms are relieved by drinking orange juice.  During a recent episode, the patient’s blood glucose level was 32 mg/dL as measured by her husband’s home glucose meter.  Medical history includes major depression and irritable bowel syndrome.  Laboratory studies performed during the next episode of symptoms show the following results:

Which of the following is the most likely cause of this patient’s symptoms?

A 65-year-old man comes to the physician because of a non-healing ulcer on his right foot.  His past medical history is significant for recurrent high blood glucose readings for the last several years, because he has failed to comply with appropriate treatment.  His BMI is 37 kg/m².  Physical examination is significant for a bilateral symmetric decrease in vibration sensation over the feet and ankles.  Which of the following is most likely to be associated with this patient’s condition?

A 50-year-old man with polycystic kidney disease comes to the office due to constant, deep pain in his shoulders, arms, and legs.  Medical history includes long-standing hypertension treated with ramipril.  Blood pressure is 150/85 mm Hg and pulse is 78/min.  Cardiopulmonary examination is normal.  Abdominal examination shows large, palpable renal masses.  Trace bilateral lower-extremity edema is present.  Laboratory results from 2 years ago showed a blood urea nitrogen level of 25 mg/dL and a creatinine level of 2.3 mg/dL.  Current laboratory results are as follows:

Which of the following metabolic states is most likely present in this patient?

A 64-year-old man comes to the office with fatigue.  He has hypertension and poorly controlled diabetes complicated by nephropathy and peripheral neuropathy.  His renal function has declined steadily over the last few years.  On examination, his conjunctivae are pale and he has bilateral 1+ peripheral edema.  Laboratory results are as follows:

On the graph below, area “C” shows the normal relationship between serum concentrations of free calcium and parathyroid hormone.  Which of the following areas most likely represents this patient’s current metabolic state?

A 35-year-old woman comes to the office due to frequent urination.  She describes drinking excessive amounts of water due to unquenchable thirst.  She does not take any medications.  Her blood glucose level is 86 mg/dL.  A standard water deprivation test is performed.  The results of urine osmolality during 4 hours of dehydration are presented in the table below.  The patient’s plasma osmolality after 3 hours of water deprivation was found to be 298 mOsm/L, and vasopressin was then administered subcutaneously.

Which of the following is the most likely diagnosis in this patient?

A 35-year-old woman at 38 weeks gestation undergoes induction of labor.  The patient has type 2 diabetes mellitus, and her blood glucose levels were increasingly difficult to control during her third trimester despite increasing doses of insulin.  During induction, the patient develops arrest of labor and undergoes a cesarean delivery.  Apgar scores are 8 and 9 at 1 and 5 minutes, respectively.  Physical examination shows a newborn large for gestational age with a birth weight of 4.6 kg (10.1 lb).  The remainder of the examination is unremarkable, and vital signs are normal.  An hour after delivery, the newborn develops hypoglycemia.  Which of the following is most likely the cause of this newborn’s hypoglycemia?

In an animal experiment the levels of various endogenous compounds are measured in the spinal fluid after application of noxious stimuli.  One of the compounds that increase as a result of the experiment is a pentapeptide with a strong affinity to delta- and mu-receptors.  Which of the following substances is most likely to have a common molecular origin with the pentapeptide described above?

An 11-month-old boy is brought to the office due to irregular jerking movements.  His mother states that for 2 weeks he has looked pale and tired, and he has been more fussy and less playful than usual.  Temperature is 36.7 C (98 F), blood pressure is 100/60 mm Hg, pulse is 114/min, and respirations are 16/min.  Physical examination reveals spontaneous bursts of nonrhythmic conjugate eye movements in various directions.  The patient also has myoclonus involving the trunk and limbs as well as generalized hypotonia.  A right-sided, nontender, immobile abdominal mass is palpated.  There is no hepatosplenomegaly, and bowel sounds are normal.  Complete blood count reveals anemia, and urine is positive for elevated levels of catecholamine breakdown products.  Which of the following is the most likely diagnosis?

A 55-year-old man comes to the office for follow-up of abnormal serum chemistries found on routine laboratory testing.  He has a history of hypertension, for which he is being treated with pharmacologic therapy, weight loss, and dietary salt restriction.  Blood pressure is 130/80 mm Hg and pulse is 80/min.  BMI is 27 kg/m².  Physical examination reveals no abnormalities.  Laboratory studies are as follows:

Which of the following is most likely responsible for these findings?

A group of researchers is developing new drugs for osteoporosis.  They are testing a new drug, Substance X, that exhibits the following metabolic effects when given via an infusion in varying doses (as shown in the graphs below).

Which of the following most closely resembles the metabolic effects of Substance X?

A 49-year-old man comes to the office due to “aching bones.”  He has a 2-month history of insidious-onset pain that is most pronounced in the back, pelvis, and lower extremities.  The pain is dull and increases after weight-bearing activities.  The patient has no prior medical conditions and takes no medications.  He emigrated from Central Africa 5 years ago and works overnight shifts as a cab driver.  Vital signs are within normal limits.  Physical examination shows normal muscle strength in the upper and lower extremities bilaterally.  A thorough laboratory evaluation establishes the diagnosis.  After discussing the likely cause of his condition, the patient starts spending more time outdoors in the sun.  Which of the following enzymatic steps will most likely be affected by this change in activity?