A 31-year-old woman, who has two healthy children, notes that she has had no menstrual periods for the past 6 months, but she is not pregnant and takes no medications. Within the past week, she has noted some milk production from her breasts. She has been bothered by headaches for the past 3 months. After nearly hitting a bus while changing lanes driving her vehicle, she is concerned with her vision. An optometrist finds her lateral vision to be reduced. On physical examination she is afebrile and normotensive. Which of the following laboratory test findings is most likely to be present in this woman?
A Increased serum cortisol
B Lack of growth hormone suppression
C Increased serum alkaline phosphatase
F Abnormal glucose tolerance test
G Decreased serum TSH
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A 28-year-old woman has had difficulty concentrating at work for the past month. She is constantly getting up and walking around to visit co-workers. She complains that the work area is too hot. She seems nervous and often spills her coffee. She has been eating more but has lost 5 kg in the past 2 months. On physical examination her temperature is 37.5°C, pulse 101/minute, respiratory rate 22/minute, and blood pressure 145/85 mm Hg. Which of the following laboratory findings is most likely to be present in this woman?
A Decreased catecholamines
B Decreased iodine uptake
C Decreased plasma insulin
D Decreased TSH
E Increased ACTH
F Increased calcitonin
A 19-year-old previously healthy woman has had a mild pharyngitis followed by a high fever over the past 24 hours. When seen in the emergency room, her skin now shows extensive areas of purpura. Vital signs include temperature 39°C, pulse rate 102/minute, respiratory rate 21/minute, and blood pressure 80/55 mm Hg. Laboratory studies show a serum sodium of 115 mmol/L, potassium 5.3 mmol/L, chloride 92 mmol/L, CO2 22 mmol/L, glucose 42 mg/dL, and creatinine 1.1 mg/dL. Which of the following is the most likely diagnosis?
A Idiopathic adrenalitis
B Disseminated tuberculosis
C Reactive systemic amyloidosis
D Sheehan syndrome
A 40-year-old woman has noted enlargement of her anterior neck region over the past 8 months. On physical examination her vital signs include T 36.8°C, P 64/minute, RR 16/minute, and BP 155/105 mm Hg. There is diffuse, symmetrical thyroid enlargement without tenderness. A chest radiograph is normal. Fine needle aspiration of the thyroid yields cells consistent with a neoplasm. Laboratory studies show that she is euthyroid, but her serum ionized calcium is elevated. She is taken to surgery and frozen sections of several thyroid masses show a malignant neoplasm composed of polygonal cells in nests. A thyroidectomy is performed. Immunostaining for calcitonin of the permanent sections is positive, and the neoplasm has an amyloid stroma with Congo red staining. Which of the following neoplasms is she most likely to have?
A Anaplastic carcinoma
B Medullary carcinoma
C Papillary thyroid carcinoma
D Metastatic renal cell carcinoma
E Parathyroid carcinoma
F Follicular carcinoma
A 37-year-old man experiences abdominal pain, nausea, and constipation for the past 3 days. On physical examination he has no palpable abdominal masses and bowel sounds are present. His lungs are clear to auscultation. He has a heart rate of 80/min with an irregular rhythm. An electrocardiogram demonstrates a shortened QT(corrected) interval and a prolonged PR interval. He has a stool positive for occult blood. Upper GI endoscopy reveals multiple 1 cm diameter shallow ulcerations of the gastric antrum. Which of the following laboratory test findings is most likely to be present in this man?
A Thyroid peroxidase antibody of 4 IU/mL
B Serum calcium of 12.4 mg/dL
C Blood glucose of 225 mg/dL
D Total serum thyroxine of 21 ng/mL
E Plasma cortisol of 45 microgm/dL at 8 am
F Urine normetanephrine of 692 microgm/gm of creatinine
G Plasma renin activity (upright) of 6.8 ng/mL/hr
A 55-year-old woman has had a 4 kg weight loss over the past 3 months. She exhibits decreased mentation over the past 10 days. On physical examination she is afebrile and hypotensive. Bilateral papilledema is noted. A head CT scan shows marked diffuse cerebral edema with effacement of the lateral ventricles. Laboratory studies show a sodium of 108 mmol/L, potassium 4.0 mmol/L, chloride 83 mmol/L, CO2 14 mmol/L, glucose 82 mg/dL, and creatinine 0.5 mg/dL. Which of the following is most likely to cause these findings?
A Small cell lung carcinoma
B Blunt head trauma
C Hypothalamic glioma
E Pituitary macroadenoma
A 29-year-old primigravida who received no prenatal care has marked vaginal bleeding after the onset of labor at 38 weeks gestation. Cesarean section is performed and a lacerated low-lying placenta is removed. She remains hypotensive for 6 hours and requires transfusion of 12 packed RBC units. Postpartum, she becomes unable to breast-feed the infant. She does not have a resumption of normal menstrual cycles. She becomes more sluggish and tired. Laboratory findings include hyponatremia, hyperkalemia, and hypoglycemia. Which of the following pathologic lesions is she most likely to have had following delivery?
A Bilateral adrenal hemorrhage
B Pituitary necrosis
C Subacute thyroiditis
D Metastatic choriocarcinoma
A 58-year-old man with a history of diabetes mellitus has noted the presence of bone pain, especially of his hands, for the past 6 months. On physical examination there is no swelling or redness of his hands, no joint deformity, but the range of motion is slightly decreased. Laboratory studies show sodium 139 mmol/L, potassium 4.0 mmol/L, chloride 98 mmol/L, C02 22 mmol/L, glucose 153 mg/dL, creatinine 7.8 mg/dL, calcium 7.8 mg/dL, phosphorus 5.7 mg/dL, total protein 6.2 g/dL, and albumin 4.0 g/dL. Which of the following conditions is this man most likely to have?
A Adrenal adenoma
B Medullary thyroid carcinoma
C Extra-adrenal pheochromocytoma
D Parathyroid hyperplasia
E Pituitary adenoma
A 49-year-old woman has had increasing cold intolerance, weight gain of 4 kg, and sluggishness over the past two years. A physical examination reveals dry, coarse skin and alopecia of the scalp. Her thyroid is not palpably enlarged. Her serum TSH is 11.7 mU/L with thyroxine of 2.1 micrograms/dL. A year ago, anti-thyroglobulin and anti-microsomal autoantibodies were detected at high titer. Which of the following thyroid diseases is she most likely to have?
A DeQuervain disease
B Papillary carcinoma
C Hashimoto thyroiditis
D Multinodular goiter
E Graves disease
A clinical study is performed with subjects who were diagnosed with hyperthyroidism, compared with a control group of subjects who were euthryoid. The pathologic findings in the thyroid glands of these subjects are analyzed to determine the spectrum of disease processes present. Which of the following pathologic processes is most likely to be found with equal frequency in both the study and the control subjects?
A Subacute granulomatous thyroiditis
B Multinodular goiter
C Medullary carcinoma
D Hashimoto thyroiditis
E Follicular adenoma
A 48-year-old woman has experienced constant back pain exacerbated by movement over the past month. She reports increasing weakness over the past 3 months. On physical examination her blood pressure is 165/110 mm Hg. She is overweight, with a BMI of 28. A radiograph of the spine reveals a compressed fracture at T10. Laboratory findings include a serum glucose of 155 mg/dL. Which of the following pathologic lesions is most likely to explain her findings?
A Adrenal cortical carcinoma
B Anaplastic thyroid carcinoma
C Empty sella syndrome
E Multinodular goiter
A 33-year-old woman has noted a weight gain of 6 kg over the past year. She has normal menstrual periods. On physical examination her blood pressure is 170/105 mm Hg. Her skin shows marked plethora. Abdominal striae are present. A serum electrolyte panel shows sodium 141 mmol/L, potassium 4.4 mmol/L, chloride 100 mmol/L, CO2 25 mmol/L, glucose 181 mg/dL, and creatinine 1.0 mg/dL. Which of the following radiologic findings would you most expect to be present in this patient?
A 2 cm right adrenal mass with abdominal CT scan
B 4 cm mass at aortic bifurcation with MR imaging
C Multiple pulmonary nodules on chest radiograph
D 10 cm cystic right ovarian lesion by abdominal ultrasound
E 2 cm "hot" thyroid nodule with Tc99 scintigraphic scan
An 35-year-old woman has had insomnia for the past 4 months, as well as episodes of diarrhea with up to 4 loose stools per day. On physical examination, she exhibits bilateral proptosis. Her outstretched hands have a fine tremor. On palpation of her neck, the thyroid gland does not appear to be enlarged and no masses are palpable. Laboratory studies show a serum TSH of 8.8 microU/mL in association with a serum total thyroxine of 15.1 microgram/dL. Which of the following is the most likely diagnosis?
A Graves disease
B Pituitary adenoma
C Chronic thyroiditis
D Prior thyroidectomy
A 25-year-old woman has had a 7 kg weight loss over the past 6 months without dieting or trying to lose weight. On physical examination she appears anxious and worried. Her hands are warm and tremulous. Vital signs show her temperature to be 37.4°C, pulse 105/minute, respirations 23/minute, and blood pressure 135/75 mm Hg. Serum laboratory data include glucose 78 mg/dL and creatinine 0.8 mg/dL. Which of the following additional laboratory test findings is most likely to be present in this woman?
A Plasma cortisol of 40 microgm/dL at 8 am
B Serum antinuclear antibody of 1:256
C Urinary free catecholamines of 500 microgm/24 hr
D Serum gastrin of 200 pg/mL
E Serum total thyroxine of 14 microgm/dL
A 50-year-old man has episodic headaches for 3 months. On physical examination his blood pressure is 185/110 mm Hg, with no other remarkable findings. Laboratory studies show sodium 145 mmol/L, potassium 4.3 mmol/L, chloride 103 mmol/L, C02 26 mmol/L, glucose 91 mg/dL, and creatinine 1.3 mg/dL. An abdominal CT scan shows a 7 cm left adrenal mass. During surgery, as the left adrenal gland is removed, there a marked rise in blood pressure. Which of the following laboratory test findings most likely explains his findings?
A Decreased serum cortisol
B Decreased urinary homovanillic acid
C Increased serum ACTH
D Increased urinary free catecholamines
E Elevated serum ANCA
A 47-year-old woman feels a "lump" in her neck that she didn't notice 5 months before. Her physician palpates a firm nodule about 2 cm in size to the left of midline in the region of the thyroid gland. By scintigraphic scanning this nodule appears "cold" with normal activity in the surrounding normally sized thyroid gland. Which of the following is the most likely diagnosis?
A Papillary carcinoma
B Follicular adenoma
C Thyroglossal duct cyst
D Toxic nodular goiter
E Granulomatous thyroiditis
F Hashimoto thyroiditis
A 56-year-old woman has had diffuse, dull, constant abdominal pain for the past 2 months. On physical examination no abnormal findings are noted. An abdominal CT scan shows a 3 cm right adrenal mass. The right adrenal is excised and on microscopic examination the mass is composed of cells resembling adrenal cortex. Which of the following features is the most reliable indicator that this mass is malignant?
A Cellular atypia
B Presence of mitoses
D Size of the mass
E Cellular necrosis
A 49-year-old woman has had multiple episodes of lower abdominal pain for the past year. On 3 occasions she passed a urinary tract stone during or following an episode of pain. During the past month she has had pain in her right middle finger. On physical examination there is pain on palpation of her right 3rd proximal phalanx. Laboratory studies show a serum calcium of 13.7 mg/dL, phosphorus of 1.9 mg/dL, creatinine 1.1 mg/dL, and albumin 4.8 g/dL. Which of the following bone lesions is she most likely to have?
A Osteitis fibrosa cystica
B Osteoid osteoma
A 40-year-old woman notes increasing enlargement and discomfort in her neck over the past week. The nurse practitioner palpates diffuse, symmetrical enlargement with tenderness in the region of the thyroid gland. Thyroid function tests show serum TSH of 0.8 mU/L and thyroxine of 11.9 micrograms/dL. She is referred to an endocrinologist, but the next available appointment is in 8 weeks. When examined by the endocrinologist her thyroid is no longer palpable and there is no pain. Repeat thyroid function tests reveal a serum TSH of 3.8 mU/L and thyroxine of 5.7 micrograms/dL. Which of the following thyroid diseases is most likely to produce these findings?
A Nodular goiter
B Non-Hodgkin lymphoma
C DeQuervain disease
F Riedel thyroiditis
G Iodine deficiency
A 33-year-old previously healthy man has lateral visual field deficits, but his residual vision is 20/20. His facial features have changed over the past year. His shoe size has increased. A head CT scan reveals enlargement of the sella turcica. Which of the following hormones is most likely being secreted in excessive amounts in this man?
A Antidiuretic hormone
D Growth hormone
E Luteinizing hormone
A 47-year-old woman has felt a "lump" in her neck for the past 2 months. On physical examination there is a firm nodule in the right lobe of her thyroid. Following fine needle aspiration and cytologic diagnosis of a neoplasm, a thyroidectomy is performed. Grossly, there is a 3 cm mass in the right lower pole that on sectioning is cystic and has papillary excrescences. Which of the following microscopic pathologic findings is most typical for this lesion?
A Giant cells
B Amyloid stroma
C Small thyroid follicles
D Clear nuclear chromatin
E Pleomorphic spindle cells
The mother of an 11-month-old infant had noted enlargement of the baby's abdomen within the past month. This is confirmed by the osteopathic physician, who notes that the baby is otherwise normally developed. An abdominal CT scan reveals a 6 cm mass, with some scattered calcifications, above the right kidney. Laboratory studies show a greatly elevated urinary vanillylmandelic acid (VMA), while the urinary homovanillic acid (HVA) is only slightly increased. The mass is removed and microscopically is composed of sheets of small blue cells. What is the most likely diagnosis?
A Congenital adrenal hyperplasia
B Adrenal cortical carcinoma
D Non-Hodgkin lymphoma
A 53-year-old woman has pain in her neck for the past month. On physical examination her vital signs include T 37°C, P 77/minute, RR 16/minute, and BP 130/80 mm Hg. There is an irregular firm mass palpable in her left neck. A CT scan shows an infiltrative mass involving the left lobe of the thyroid and extending into adjacent soft tissues. Laboratory studies show TSH 2.9 mU/L, total serum thyroxine 8.6 microgm/dL, calcium 8.7 mg/dL, and phosphorus 2.8 mg/dL. A fine needle aspiration biopsy of the mass shows malignant spindle-shaped cells present that demonstrate a p53 mutation immunohistochemically. Which of the following neoplasms is this woman most likely to have?
B Follicular carcinoma
E Papillary carcinoma
F Parathyroid carcinoma
A 45-year-old man has a 4 month history of nonfocal, generalized headaches. On physical examination he is found to have a blood pressure of 170/110 mm Hg. Laboratory studies show a serum sodium of 146 mmol/L, potassium 2.3 mmol/L, chloride 103 mmol/L, CO2 27 mmol/L, glucose 82 mg/dL, and creatinine 1.2 mg/dL. His plasma renin activity is 0.1 ng/mL/hr and his serum aldosterone 65 ng/mL. Which of the following is the most likely cause for his findings?
A 21-hydroxylase enzyme deficiency
B Adrenal cortical adenoma
C Pituitary adenoma
D Exogenous corticosteroid administration
E Renal cell carcinoma
A 40-year-old woman has noted painless swelling of her neck for the past 3 weeks. On physical examination there is diffuse enlargement of her thyroid. Laboratory studies show an increased titer of anti-thyroid peroxidase and anti-thyroglobulin antibodies. Within a month, the swelling has diminished. Which of the following complications is she most likely to develop?
C Non-Hodgkin lymphoma
D Papillary carcinoma
E Riedel thyroiditis
A 45-year-old woman with severe rheumatoid arthritis has been on chronic corticosteroid therapy for the past 15 years. She is admitted for an orthopedic procedure to correct joint deformity from her disease. She continues to receive her regular dosage of 5 mg of prednisone per day. Three days postoperatively, she develops an aspiration pneumonia with Klebsiella pneumoniae cultured from sputum. Five days following the surgery, she becomes obtunded. Laboratory findings at that time include: sodium 105 mmol/L, potassium 5.4 mmol/L, chloride 87 mmol/L, CO2 16 mmol/L, glucose 40 mg/dL, and creatinine 1.1 mg/dL. Which of the following complications is most likely to have occurred in this patient?
A Anterior pituitary necrosis
B Waterhouse-Friderichsen syndrome
C Acute Addisonian crisis
D Conn syndrome
E 21-hydroxylase deficiency
A 38-year-old woman has had a feeling of fullness in her neck for the past year. She is otherwise asymptomatic. Her physician's assistant palpates a symmetrically enlarged but nontender thyroid gland. She has no difficulty swallowing. There is no palpable lymphadenopathy. She is afebrile. Her serum TSH is 3.5 mU/L with total thyroxine of 8.2 micrograms/dL. Thyroid peroxidase antibody is not detected. Two years later, her thyroid has not appreciably changed in size. Which of the following conditions is she most likely to have?
B Nodular goiter
D Anaplastic carcinoma
F Papillary carcinoma
A 15-year-old boy has had worsening headaches for 2 months. On examination he has diminished peripheral vision, but no loss of visual acuity. A head CT scan reveals a 4 cm mass expanding the sella turcica and eroding the sphenoid bone. The mass is cystic with scattered calcifications. Which of the following is the most likely diagnosis?
B Metastatic seminoma
D Anaplastic astrocytoma
A 52-year-old man has weight of 4 kg over the past 6 months, along with bruises on his skin with even minor trauma and back pain. He has smoked 2 packs a cigarettes per day for 35 years. On physical examination he has obesity in a truncal distribution, plethora, and a blood pressure of 160/110 mm Hg. A radiograph of the spine reveals a compressed fracture of T11. Which of the following neoplasms is he most likely to have?
A Pheochromocytoma of bladder
B Follicular carcinoma of thyroid
C Osteosarcoma of femur
D Small cell anaplastic carcinoma of lung
E Neuroendocrine carcinoma of pancreas
A 41-year-old man has been drinking large quantities of water--up to 20 liters per day--for the past week. On physical examination he has diminished skin turgor and dry mucous membranes. Laboratory studies show sodium 162 mmol/L, potassium 4.1 mmol/L, chloride 121 mmol/L, and bicarbonate 27 mmol/L. His serum glucose is 75 mg/dL and creatinine 1.0 mg/dL. His serum osmolality is 343 mOsm/kg. A deficiency of which of the following hormones is most likely present in this man?
A 50-year-old man has a lump on his neck found at physical examination. A fine needle aspirate of this lump shows a follicular neoplasm of the thyroid. He undergoes a total thyroidectomy. Within a day following surgery, he is noted to have tingling sensations and neuromuscular irritability. Which of the following serum laboratory tests should be ordered immediately to determine further therapy for this man?
A 30-year-old woman from Barcelona has noted enlargement of her neck over the past 4 months. On physical examination, she has a diffusely enlarged thyroid that is not painful to palpation. Her TSH level is 0.2 mU/L. A subtotal thyroidectomy is performed and histologically the tissue shows follicles with papillary infoldings lined by tall columnar cells. Which of the following is the most likely diagnosis?
C Multinodular goiter
A 57-year-old man is found comatose. On physical examination he has decreased skin turgor. Laboratory studies show a blood glucose of 780 mg/dL. Urinalysis reveals no ketosis or proteinuria, though there is 4+ glucosuria. Which of the following is the most likely diagnosis?
A Neuroendocrine tumor secreting glucagon
B Type I diabetes mellitus
C Cushing syndrome
D Ingestion of a large quantity of sugar
E Type II diabetes mellitus
A 23-year-old man wants to increase his muscle mass for playing physical contact sports. He attempts to accomplish this by injections of a substance obtained from a 'friend'. Over the next year he develops acne, icterus, and increased fatigue. An infertility workup reveals hypospermia. Laboratory studies show Hgb 19.2 g/dL, Hct 58.1.4%, platelet count 330,300/microliter, and WBC count 7410/microliter. Which of the following neoplasms is he at greatest risk for developing in the future?
A Hepatocellular carcinoma
C Renal cell carcinoma
A 33-year old woman has had increased anxiety with headaches and diaphoresis over the past 2 months. On physical examination she is afebrile, with a heart rate of 90/minute and blood pressure 150/90 mm Hg. Laboratory studies show elevated urinary catecholamines, elevated plasma renin activity, and normal TSH. Her plasma cortisol level is normal. An abdominal CT scan is performed. At which of the following locations is a mass lesion most likely to be found?
A Aortic bifurcation
B Hepatic capsule
C Pancreatic tail
E Splenic hilum
A 2-year-old child living in Odessa is small for its age and exhibits profound intellectual disability. On physical examination he has dry, coarse skin. Which of the following pathologic features involving the thyroid gland is this child most likely to have?
A Papillary adenoma
B Diffuse hyperplasia
C Granulomatous inflammation
D Metastatic carcinoma
E Marked atrophy
A 35-year-old G3 P3 woman has increasing fullness in her neck for the past 5 months since delivery of her last infant. On physical examination her thyroid gland is diffusely enlarged but not painful to palpation. Laboratory studies show an anti-thyroglobulin titer of 1:256 and an anti-thyroid peroxidase titer of 1:512. Her TSH and thyroxine are normal. Which of the following is the most likely diagnosis?
A Riedel thyroiditis
B Adenovirus infection
C Subacute lymphocytic thyroiditis
E Subacute granulomatous thyroiditis
F Diffuse goiter
A clinical study is performed involving subjects who developed Addision disease. They were recorded to have laboratory studies with hyponatremia, hyperkalemia, hypoglycemia, and decreased plasma cortisol. They became hypotensive. In some subjects, this disease had an acute onset over less than 2 days' time. Which of the following conditions is most likely to produce this acute course?
A Waterhouse-Friderichsen syndrome
B Metastatic small cell anaplastic carcinoma
C Disseminated Mycobacterium tuberculosis infection
D Reactive systemic amyloidosis
E Blunt force abdominal trauma
A 39-year-old woman has noted discomfort with fullness to her neck over the past year. On physical examination she is afebrile and normotensive. There is irregular enlargement of her thyroid gland, but no tenderness on palpation. A scintigraphic scan shows normal uptake except for increased uptake in a 1 cm area in the left lower lobe. Her anti-thyroid peroxidase antibody is negative. Which of the following complications is she most likely to develop?
C Graves disease
D Subacute thyroiditis
A 42-year-old man has enlargement of his neck for the past 7 months. He is concerned, because a sister and maternal aunt had thyroid cancer. On physical examination, his thyroid is palpably nodular but nontender. A fine needle aspiration biopsy is performed and cytologic examination shows cells present consistent with a neoplasm. He undergoes total thyroidectomy. Sectioning the resected thyroid reveals four distinct tumor masses from 0.5 to 3 cm in size. These masses are solid and firm, with a tan cut surface. On microscopic examination an immunostain for calcitonin is positive in the nests of dark blue cells of these masses. He is at greatest risk for developing which of the following neoplasms in the future?
A 17-year-old girl with Goodpasture syndrome progressed to chronic renal failure and was placed on chronic hemodialysis. She developed severe hypertension. However, she had difficulty accepting the reality of her disease, and she missed dialysis appointments and did not take her antihypertensive medication regularly. Laboratory studies now show her serum ionized calcium is 5.9 mg/dL with phosphorus 6.2 mg/dL and albumin 3.6 g/dL. Which of the following complications of her illness is she most likely to have?
C Skin rash
E Joint pain
A 1-year-old male child has been irritable for the past day. On physical examination he has a right inguinal hernia with incarceration of a loop of small intestine. A laparotomy is performed and the defect is closed. The tissue from the hernia sac is excised. The surgical pathology report indicates the presence of a focus of adrenal cortex in the excised hernia sac. Which of the following is the most likely diagnosis?
B Adrenal cortical carcinoma metastasis
C Incidental ectopia
D Risk for subsequent adrenocortical insufficiency
E Multiple endocrine neoplasia syndrome
A 14-year-old boy has felt a "bump" in his neck for the past year. On physical examination just anterior to the trachea in the midline is a palpable non-tender 2 cm mass. A fine needle aspirate of the mass yields only clear, mucoid fluid. Which of the following is the most likely diagnosis?
A Thyroglossal duct cyst
B Lymph node metastasis of follicular carcinoma
C Follicular adenoma
D Nodule of a multinodular goiter
E Branchial cleft cyst
A clinical study is performed of subjects from birth to age 80 years who were documented by laboratory testing to have hypocalcemia. The medical records of these subjects are analyzed and the disease conditions documented in these subjects recorded. A subset of these patients had hypocalcemia documented in infancy. Which of the following conditions is most likely to have been present in this subset of patients?
A Parathyroid carcinoma
B Vitamin D deficiency
C Chronic renal failure
D DiGeorge syndrome
E Parathyroid adenoma
A 5-month-old female infant was the product of an uncomplicated pregnancy and was born at term. However, the baby has failure to thrive. On physical examination there is clitoral hypertrophy and poor skin turgor. The baby appears neurologically normal. Laboratory studies show serum sodium 116 mmol/L, potassium 6.2 mmol/L, chloride 83 mmol/L, and CO2 22 mmol/L. There is no history of diarrhea or vomiting. Which of the following inborn errors of metabolism is this infant most likely to have?
A 21-hydroxylase deficiency
B Phenylalanine transferase deficiency
C Galactose-1-uridyl transferase deficiency
D Glucose-6-phosphatase deficiency
E Iodine peroxidase deficiency
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