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Lecture

Disorders of sexual differentiation, Klinefelter's, Turner's, mixed gonadal dysgenesis, pseudohermaphroditism, freemartinism, Kallmann Syndrome, endocrine disruption

7 Pages
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Department
Biomedical Science
Course Code
BMS 460
Professor
D.Rao Veeramachaneni

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4 December
Disorders of Sexual Differentiation
“Intersex,” “imposex”
Broadly classified as disorders of gonadal differentiation and development,
pseudohermaphorditism, or unclassified/miscellaneous forms
Disorders of Gonadal Differentiation and Development
47, XXY; also 48, XXYY or mosaic 46, XY/46 XXXY: Klinefelter’s
Most common major abnormality; seminiferous tubule dysgenesis
46, XX males: sex reversal
Probably translocation of Y material to X chromosome or mutation of a X chr
gene
Normal testes and external genitalia but 10% have hypospadias
45, XO: Turners
Oocytes degenerate leaving streak gonads at birth
46, XX: pure gonadal dysgenesis
Similar to Turner’s syndrome but no somatic effects
Requires estrogen and progesterone replacement therapy
45, XO/46, XY mosaicism: mixed gonadal dysgenesis
Mostly phenotypic females but entire spectrum covered
45, XO/46, XY or 46, XY: dysgenetic male pseudohermaphorditism
Bilateral dysgenetic testes; increased risk of gonadoblastoma (45% at 40 year)
Produce some T and MIS; spectrum of Mullerian and Wolffian structures persist
46, XY: complete gonadal dysgenesis
Male genotype, SRY dysfunctional; phenotypic female with sexual infantilism
Increased risk of germ cell tumors; manage with gonadectomy and hormone
replacement
46, XY: embryonic testicular regression
Evidence of prior testicular function
May be mutation or teratogen or bilateral torsion
True hermaphroditism
Both ovarian and testicular tissue in the form of one of each or one/two ovotestes
Internal differentiation depends on the function of ipsilateral gonad
Much more common in pigs than in any other domestic mammals
Klinefelter’s Syndrome
47, XXY
X-inactivation
Barr body
1 in 500
Most frequent cause of hypogonadism
Some instances of cryptorchidism
Azoospermia
Micropenis
Small, firm testes
Hyalinization of seminiferous tubules
Loss of Sertoli cells; ↓ inhibin
↑ FSH; stimulates aromatase in LC
↑ Estrogen
↓ T; ↑ LH; LC hyperplasia
Leydig cell nodules (LCN)
Gynecomastia
Breast development
Turner’s Syndrome
45, X gonadal dysgenesis
45, XO
No Barr body
1:2500
Most spontaneously abort

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Description
4 December Disorders of Sexual Differentiation “Intersex,” “imposex” Broadly classified as disorders of gonadal differentiation and development, pseudohermaphorditism, or unclassified/miscellaneous forms Disorders of Gonadal Differentiation and Development 47, XXY; also 48, XXYY or mosaic 46, XY/46 XXXY: Klinefelter’s Most common major abnormality; seminiferous tubule dysgenesis 46, XX males: sex reversal Probably translocation of Y material to X chromosome or mutation of a X chr gene Normal testes and external genitalia but 10% have hypospadias 45, XO: Turner’s Oocytes degenerate leaving streak gonads at birth 46, XX: pure gonadal dysgenesis Similar to Turner’s syndrome but no somatic effects Requires estrogen and progesterone replacement therapy 45, XO/46, XY mosaicism: mixed gonadal dysgenesis Mostly phenotypic females but entire spectrum covered 45, XO/46, XY or 46, XY: dysgenetic male pseudohermaphorditism Bilateral dysgenetic testes; increased risk of gonadoblastoma (45% at 40 year) Produce some T and MIS; spectrum of Mullerian and Wolffian structures persist 46, XY: complete gonadal dysgenesis Male genotype, SRY dysfunctional; phenotypic female with sexual infantilism Increased risk of germ cell tumors; manage with gonadectomy and hormone replacement 46, XY: embryonic testicular regression Evidence of prior testicular function May be mutation or teratogen or bilateral torsion True hermaphroditism Both ovarian and testicular tissue in the form of one of each or one/two ovotestes Internal differentiation depends on the function of ipsilateral gonad Much more common in pigs than in any other domestic mammals Klinefelter’s Syndrome 47, XXY X-inactivation Barr body 1 in 500 Most frequent cause of hypogonadism Some instances of cryptorchidism Azoospermia Micropenis Small, firm testes Hyalinization of seminiferous tubules Loss of Sertoli cells; ↓ inhibin ↑ FSH; stimulates aromatase in LC ↑ Estrogen ↓ T; ↑ LH; LC hyperplasia Leydig cell nodules (LCN) Gynecomastia Breast development Turner’s Syndrome 45, X gonadal dysgenesis 45, XO No Barr body 1:2500 Most spontaneously abort Streak ovaries No oogenesis Risk of dysgerminoma ↓ E; ↑ FSH and LH The most common gonadal disorder causing primary amenorrhea Short stature; webbed neck; wide-spacing of nipples Mixed Gonadal Dysgenesis Note that short stature and streak ovaries, which lack germinal tissue, are associated with other forms of gonadal dysgenesis but not with somatic abnormalities (epicantal folds, low-set ears, webbed neck, lymphedema of the hands and feet, renal malformations, and coarctation [narrowing] of the aorta) as found in Turner’s. Pseudohermaphroditism A state in which the gonads are of one sex, but one or more contradictions exist in the morphologic criteria of sex In female pseudohermaphroditism, the individual is genetically female and has female gonads (ovaries) but has significant male secondary sex characteristics. Most common cause: congenital adrenal hyperplasia Rarely: maternal ingestion of androgen or virilizing tumors in the mother In male pseudohermaphroditism, the individual is genetically male and has male gonads (testes) but has significant female secondary sex characteristics. Leydig cell aplasia Disorders of T biosynthesis Androgen receptor defects Impaired AMH/MIS production and/or action Male Pseudohermaphroditism Deficiency of androgen synthesis, conversion, or action Ambiguous genitalia Impaired testosterone synthesis 3β-Hydroxysteroid dehydrogenase deficiency Inhibition of enzymes Endocrine disruptors; e.g., phthalates Impaired conversion of testosterone to DHT 5α-Reductase deficiency Inhibition of enzymes Pharmaceuticals; e.g., Proscar Impaired binding of androgen to its receptor Androgen receptor deficiency Androgen insensitivity syndrome/testicular feminization syndrome Androgen receptor antagonism Pesticides; e.g., p.p’-DDT and its metabolites Deficiency of androgen receptor Androgen insensitivity/testic
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