Questions and Answers
What is the biochemical result of Leydig cell dysfunction in Klinefelter's Syndrome?
What process aids the diagnosis of Klinefelter's Syndrome using a buccal smear?
In Klinefelter's Syndrome, what does increased LH concentrations stimulate?
Which tissues or fluids can be used for karyotyping to diagnose Klinefelter's Syndrome?
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What is the main type of therapy for Klinefelter's Syndrome?
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A defect in which origin is a common cause of male reproductive dysfunction?
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What is a common clinical presentation of male reproductive dysfunction in adult males?
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Which clinical feature is associated with hypogonadism that occurs before puberty?
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What is one of the common problems that can lead to male reproductive dysfunction?
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Which laboratory test result indicates gonadal dysfunction in male hypogonadism?
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Which of the following is a cause of primary male hypogonadism?
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What is a psychological effect of male hypogonadism?
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What hormone level is most useful in the laboratory assessment of male hypogonadism?
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Male sexual development is determined by which chromosome combination?
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At what point in gestation do embryos of both sexes develop identically?
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Which hormone is responsible for the formation of the prostate, urethra, and external genitalia?
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Which enzyme converts testosterone to dihydrotestosterone?
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What percentage of serum testosterone is bound to SHBG?
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Which hormone acts on wolffian structures to form internal genitalia?
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Where is testosterone metabolized?
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What is one of the functions of testosterone during puberty?
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What can rule out hypogonadism in most cases?
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What condition involves early sexual development before age 9 years?
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Which condition is characterized by insensitivity to androgens?
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What is the normal response of LH to a GnRH test in terms of its basal level?
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Which syndrome results from the multiplication of X chromosomes?
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Which feature is common in patients with Klinefelter's syndrome?
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In androgen insensitivity, what hormonal levels are typically elevated?
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Which of the following is NOT typically associated with Klinefelter's syndrome?
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Study Notes
Klinefelter's Syndrome
- Caused by multiplication of X chromosome: XXY, XXXY, XXXXY
- Occurs in 1:400 males
- Characterized by:
- Hypogonadism with small, firm testes
- Gynaecomastia
- Elevated gonadotrophins
- Reduced serum testosterone due to sclerosis of the seminiferous tubules
- Biochemical features:
- Leydig cell dysfunction results in reduced testosterone production and compensatory increase in serum LH
- Increased LH concentrations stimulate Leydig cell secretion of estradiol, producing variable degrees of feminization and gynecomastia
- Total testosterone is frequently in the low normal range, although classically it is below normal
- Diagnosis aided by:
- Examination of a buccal smear for Barr bodies
- Karyotyping on bone marrow, amniotic fluid, foetal cells, skin, solid tumours, and testicular tissue or blood lymphocytes
- Treatment consists of androgen replacement
Male Hypogonadism
- Can be caused by a defect of either:
- Hypothalamic origin
- Pituitary origin
- Testicular origin
- Common problems:
- Chronic renal failure
- Orchitis
- Drugs
- Cancer of the testis
- Clinical presentation:
- Erectile dysfunction
- Infertility
- Loss of libido
- Classification:
- Primary - testicular
- Secondary - hypothalamic or pituitary
- Clinical features:
- Depends on the age of onset
- Hypogonadism in the second to third month of foetal life results in ambiguous genitalia
- Hypogonadism before puberty results in failure of secondary sexual development
- There may also be a decrease in muscle mass with diminished muscle strength and endurance
- The voice is high pitched because of the failure of thickening and maturation of the vocal cords
- Infantile genitalia
Laboratory Tests
- Most important tests - serum testosterone, FSH, LH, and SHBG
- Serum prolactin and estradiol levels may be useful
- Most patterns are easy to understand
- Low testosterone with high gonadotrophins indicates gonadal dysfunction
- Low testosterone with low gonadotrophins indicates pituitary/hypothalamic dysfunction
- Hyperprolactinaemia may result in suppression of testosterone secretion
- With the androgen insensitivity states, there are elevations of both testosterone and gonadotrophins
GnRH Test
- Stimulates secretion of LH and FSH
- Test of pituitary function
- Intravenous injection of 100ug GnRH
- LH and FSH is measured at 15, 30, 45, and 60 minutes post-injection
- Normal response is a maximum LH of 2.5 times the basal level and maximum FSH of 2 times the basal level
Testosterone
- Functions:
- Embryologic male genital differentiation
- Maturation of the external genitals
- Skeletal muscle growth
- Deepening of the voice
- Epiphyseal cartilage growth during puberty
- Male hair growth and distribution
- Stimulation of sebaceous glands
- Male social behaviour
- Metabolised in liver and kidney
- In the periphery converted to oestradiol by aromatase; more in obesity
- Normal range is 9-28 nmol/L
- Circadian variation
Testis
- Hormone production:
- Cholesterol -> Pregnenolone -> 17-Hydroxypregnenolone -> 17-Hydroxyprogesterone -> Androstenedione -> Testosterone
- Enzymes involved:
- Desmolase
- 17 hydroxylase
- 3β hydroxysteroid dehydrogenase
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Description
This quiz covers the biochemistry and diagnosis of Klinefelter's Syndrome, including hormonal imbalances and karyotyping.