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Questions and Answers
What is the biochemical result of Leydig cell dysfunction in Klinefelter's Syndrome?
What is the biochemical result of Leydig cell dysfunction in Klinefelter's Syndrome?
- Reduced testosterone production (correct)
- Decreased serum LH
- Increased testosterone production
- Constant estradiol levels
What process aids the diagnosis of Klinefelter's Syndrome using a buccal smear?
What process aids the diagnosis of Klinefelter's Syndrome using a buccal smear?
- Examining for Barr bodies (correct)
- Identifying Leydig cells
- Testing testosterone levels
- Measuring LH levels
In Klinefelter's Syndrome, what does increased LH concentrations stimulate?
In Klinefelter's Syndrome, what does increased LH concentrations stimulate?
- Reduction in estradiol
- Production of testosterone
- Leydig cell secretion of estradiol (correct)
- Constant LH levels
Which tissues or fluids can be used for karyotyping to diagnose Klinefelter's Syndrome?
Which tissues or fluids can be used for karyotyping to diagnose Klinefelter's Syndrome?
What is the main type of therapy for Klinefelter's Syndrome?
What is the main type of therapy for Klinefelter's Syndrome?
A defect in which origin is a common cause of male reproductive dysfunction?
A defect in which origin is a common cause of male reproductive dysfunction?
What is a common clinical presentation of male reproductive dysfunction in adult males?
What is a common clinical presentation of male reproductive dysfunction in adult males?
Which clinical feature is associated with hypogonadism that occurs before puberty?
Which clinical feature is associated with hypogonadism that occurs before puberty?
What is one of the common problems that can lead to male reproductive dysfunction?
What is one of the common problems that can lead to male reproductive dysfunction?
Which laboratory test result indicates gonadal dysfunction in male hypogonadism?
Which laboratory test result indicates gonadal dysfunction in male hypogonadism?
Which of the following is a cause of primary male hypogonadism?
Which of the following is a cause of primary male hypogonadism?
What is a psychological effect of male hypogonadism?
What is a psychological effect of male hypogonadism?
What hormone level is most useful in the laboratory assessment of male hypogonadism?
What hormone level is most useful in the laboratory assessment of male hypogonadism?
Male sexual development is determined by which chromosome combination?
Male sexual development is determined by which chromosome combination?
At what point in gestation do embryos of both sexes develop identically?
At what point in gestation do embryos of both sexes develop identically?
Which hormone is responsible for the formation of the prostate, urethra, and external genitalia?
Which hormone is responsible for the formation of the prostate, urethra, and external genitalia?
Which enzyme converts testosterone to dihydrotestosterone?
Which enzyme converts testosterone to dihydrotestosterone?
What percentage of serum testosterone is bound to SHBG?
What percentage of serum testosterone is bound to SHBG?
Which hormone acts on wolffian structures to form internal genitalia?
Which hormone acts on wolffian structures to form internal genitalia?
Where is testosterone metabolized?
Where is testosterone metabolized?
What is one of the functions of testosterone during puberty?
What is one of the functions of testosterone during puberty?
What can rule out hypogonadism in most cases?
What can rule out hypogonadism in most cases?
What condition involves early sexual development before age 9 years?
What condition involves early sexual development before age 9 years?
Which condition is characterized by insensitivity to androgens?
Which condition is characterized by insensitivity to androgens?
What is the normal response of LH to a GnRH test in terms of its basal level?
What is the normal response of LH to a GnRH test in terms of its basal level?
Which syndrome results from the multiplication of X chromosomes?
Which syndrome results from the multiplication of X chromosomes?
Which feature is common in patients with Klinefelter's syndrome?
Which feature is common in patients with Klinefelter's syndrome?
In androgen insensitivity, what hormonal levels are typically elevated?
In androgen insensitivity, what hormonal levels are typically elevated?
Which of the following is NOT typically associated with Klinefelter's syndrome?
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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