Updated: 4/20/2019

Klinefelter Syndrome

Topic
Review Topic
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Questions
6
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Evidence
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https://upload.medbullets.com/topic/111078/images/klinefelter_syndrome.jpg
Snap Shot
  • A 24-year-old man with infertility is noted to have gynecomastia, atrophic testes, and azoospermia.
Overview
Introduction
  • 47 XXY resulting from nondisjunction or translocation
    • one X chromosome becomes a Barr body
  • Occurs in 1/1000 males
    • 1/100 of those who are mentally retarded
    • common cause of infertility during workup
  • Pathogenesis
    • dysgenesis of seminiferous tubules and loss of Sertoli cells
      • leads to ↓ inhibin and resultant ↑ FSH
      • FSH upregulates aromatase leading to increased conversion of androgens to estrogens  
    • Leydig cell dysfunction
      • leads to ↓ testosterone
      • without negative feedback of testosterone there is an ↑ LH
  • Diagnosis 
    • seldom made before puberty
    • Karyotyping is diagnostic test of choice
Presentation
  • Physical exam
    • hypogonadism
    • long extremities (eunuchoid body shape)
    • female hair distribution
    • gynecomastia
    • azoospermia
    • testicular atrophy
Evaluation
  • Laboratory
    • labs show elevated
      • aromatase 
Prognosis, Prevention, and Complications
  •  Testicular neoplasms
    • ↑ risk for testicular neoplasms
 

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Questions (6)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
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(M1.RP.6005) A 19-year-old male from rural West Virginia presents to his family medicine doctor to discuss why he is having trouble getting his wife pregnant. On exam, he is 6 feet 2 inches with a frail frame and broad hips for a male his size. He is noted to have mild gynecomastia, no facial hair, and small, underdeveloped testes. He claims that although he has a lower libido than most of his friends, he does have unprotected sex with his wife. His past medical history is notable for developmental delay and difficulties in school. What is the most likely chromosomal abnormality in this patient? Review Topic

QID: 106967
1

Trisomy 13

1%

(1/100)

2

Trisomy 21

0%

(0/100)

3

47: XYY

9%

(9/100)

4

47: XXY

87%

(87/100)

5

45: XO

1%

(1/100)

M1

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SUBMIT RESPONSE 4

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(M1.RP.73) A 30-year-old man presents for an infertility work-up. He and his wife have been unsuccessfully trying to get pregnant for 12 months. The patient has no known history of medical conditions. Physical exam was notable for features depicted in Figure A. Laboratory testing showed increased levels of FSH and LH.

Which of the following is the most likely explanation for this patient's presentation?
Review Topic

QID: 106542
FIGURES:
1

47 XYY chromosome disorder

1%

(1/67)

2

47 XXY chromosome disorder

69%

(46/67)

3

Chloride ion transporter defect

4%

(3/67)

4

Androgen insensitivity

19%

(13/67)

5

Defective migration of GnRH cells

1%

(1/67)

M1

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SUBMIT RESPONSE 2

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(M1.RP.27) A young Caucasian couple in their late twenties present for an infertility evaluation after trying to conceive over 2 years. On physical exam, the female appears healthy and states that she has regular menstrual cycles. The male partner is noted to have long extremities with wide hips, low muscle mass, gynecomastia, sparse facial or chest hair, and small, firm testes. Laboratory tests of the male partner reveal elevated serum LH and FSH and low testosterone levels. If cytogenetic tests were performed, which of the following would be seen in this male? Review Topic

QID: 107013
1

Presence of a barr body

82%

(28/34)

2

Absence of a barr body

6%

(2/34)

3

Absence of a second sex chromosome

6%

(2/34)

4

Trisomy of chromosome 13

3%

(1/34)

5

Trisomy of chromosome 18

0%

(0/34)

M1

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SUBMIT RESPONSE 1

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(M1.RP.1) A 25-year-old male visits his physician because of fertility issues with his wife. Physical exam reveals bilateral gynecomastia, elongated limbs, and shrunken testicles. Levels of plasma gonadotropins are elevated. Which of the following is also likely to be increased in this patient: Review Topic

QID: 101663
1

Testosterone

3%

(4/125)

2

Inhibin

34%

(42/125)

3

Aromatase

55%

(69/125)

4

Ejaculatory sperm

0%

(0/125)

5

Sertoli cells

6%

(8/125)

M1

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SUBMIT RESPONSE 3
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Topic COMMENTS (14)
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