Lecture 38 Flashcards
What are the three classifications of sexual differentiation?
- Disorders of Gonadal Differentiation and Development
- Pseudohermaphroditism
- Unclassified/Miscellaneous Forms
What are the 9 disorders of gonadal differentation and development?
- Klinefelter’s
- Sex Reversal
- Turner’s
- Pure Gonadal Dysgenesis
- Mixed Gonadal Dysgenesis
- Dysgenetic Male Pseudohermaphroditism
- Complete Gonadal Dysgenesis
- Embryonic Testicular Regression
- True Hermaphroditism
What are the karyotypes of Klinefelter’s
- 47, XXY
- 48, XXYY
- Mosaic 46, XY/47, XXY
What is the karyotype of male sex reversal?
46,XX
What is the karyotype of Turner’s?
45,X0
What is the karyotype of pure gonadal dysgenesis?
46,XX
What is the karyotype of mixed goanadal dysgenesis?
Mosaic 45,X0/46,XY
What are the karyotypes of Dysgenetic Male Pseudohermaphroditism?
- 45,X0/46,XY
- 46,XY
What is the karyotype of Complete Gonadal Dysgenesis?
46,XY
What is the karyotype of Embryonic Testicular Regression?
46,XY
What is the karyotype of True Hermaphroditism?
N/a
What is Klinefelter’s?
Most common major abnormality; seminiferous tubular dysgenesis
What is Sex Reversal?
- Probably translocation of Y material to X chromosome or mutation of a X chromosome gene
- Normal external genitalia but 10% have hypospadias
What is Turner’s?
Oocytes degenerate leaving streak gonads at birth
What is Pure Gonadal Dysgenesis?
- Similar to Turner’s syndrome but no somatic effects
- Require estrogen and progesterone replacement therapy
Who has Mixed Gonadal Dysgenesis?
Mostly phenotypic females but entire spectrum covered
What is Dysgenetic Male Pseudohermaphroditim?
- Bilateral dysgenetic testes; Increased risk of gonadoblastoma (45% at 40 years)
- Produce some T and MIS; spectrum of Mullerian and Wolffian structures persisting
What is caused by Complete Gonadal Dysgenesis?
- The male genotype is SRY dysfunctional
- The phenotypic female has sexual infantalism
- Increased risk of germ cell tumors
How is Complete Gonadal Dysgenesis managed?
- Gonadectomy
- Hormone replacement
What is Embryonic Testicular Regression?
Regressed testicle with evidence of prior function d/t perhaps mutation, teratogen or bilateral torsion
What is true hermaphroditism?
Both ovarian and testicular tissue in the form of one of each or one/two ovotestes with internal differentiation depending on the function of the ipsilateral gonad
What is the most common domestic mammal to experience true hermaphroditism?
Pigs
What are the symptoms of Klinefelter’s Syndrome?
- X-inactivation/Barr body
- Hypogonadism
- Some instances of cryptorchidism
- Azoospermia (no sperm in semen)
- Micropenis
- Small, firm testes
- Gynecomastia (breast development)
How does Klinefelter’s Syndrome cause small, firm testes?
Hyalinization of seminiferious tubules -> Loss of Sertoli cell -> decreased inhibin -> Increased FSH -> aromatase in LC stimulated -> increased E -> decreased T and increased LH -> LC hyperplasia -> Leyig cell nodules (LCN)
What is hyalinization?
Process where normal cells are replaced by a translucent, acellular matrix that gives tissues a glassy appearance under a microscope
How often does klinefelter occur in males?
1 in 500
How often does Turner’s Syndrome occur?
1 in 2500 (most spontaneously abort)
What are the symptoms of Turner’s Syndrome?
- No Barr body
- Streak ovaries -> No oogenesis (risk of dysgerminoma) -> decreased E and increased FSH and LH -> primary amenorrhea
- Short stature
- Webbed neck
- Wide-spacing of nipples
What is primary amenorrhea?
Complete absence of a mestrual period by the age of 15
What signs of Turner’s Syndrome are not shared with those from Mixed Gonadal Dysgenesis?
- Epicanthal folds
- Low-set ears
- Webbed neck
- Lymphedema of the hands and feet
- Renal malformations
- Aorta coarctation (narrowing)
What signs of Turner’s Syndrome are shared with those from Mixed Gonadal Dysgenesis?
- Short stature
- Streak ovaries (lacking germinal tissue)
How is pseudohermaphroditism characterized in females?
- Genetically female
- Female gonads
- Significant male secondary sex characteristics
How is pseudohermaphroditism characterized in males?
- Genetically male
- Male gonads
- Significant female secondary sex characteristics
Most common cause of female pseudohermaphroditism?
- Congenital Adrenal Hyperplasia
Rare causes of female pseudohermaphroditism:
Maternal ingestion of androgens or virilizing tumors in the mother
Causes of male pseudohermaphroditism:
- Leydig cell aplasia
- Disorders of T/DHT biosynthesis
- Androgen receptor defects
- Impaired AMH/MIS production and/or action
What genital structure is caused by differentiation into a female?
Ano-genital raphe
What genital structure is caused by differentiation into a male?
Urogenital raphe
How does deficiency of 3B-HSD cause male pseudohermaphroditism?
- Shuts down synthesis of cortisol and aldosterone (adrenal hyperplasia)
- Diminishes synthesis of androgens (ambiguous genitalia and cryptorchidism)
How does a mutation in 17B-HSD cause pseudohermaphroditism?
- No T -> shunts precursors primarily to E and no DHT made
- Most common cause of male pseudohermaphroditism due to defective T biosynthesis
How does the deficiency of 5a-reductase occur?
- Also known as Guevedoces/Machihembras/Turnims (“penis at 12 yr”/”First woman, then man”/”Expected to become men”)
- Autosomal recessive (2p23; only people who have mutations in both copies of the SRD5A2 gene are genetically male have the characteristic signs of 5-a reductase type II deficiency)
How does the deficiency of 5a-Reductase cause male pseudohermaphroditism?
- At 18 months, the appearance is female though undescended testes are present
- Lacking DHT in utero, this boy’s external genetalia develop as female but internal gonadal tissue is male and karyotype is normal
- In utero, DHT is essential for the normal male development of the external genitalia
- Just before puberty, phenoytype is still female
- With T surge at puberty, the phenotype changes to male
What are the differences in Guevedoces men than physiological men?
- Beard growth is scanty
- No hairline recession
- No acne
- Prostate remains small
How does the deficiency of androgen receptors cause male pseudohermaphroditism?
X-linked recessive: largest single entity that leads to 46,XY undermasculinized genitalia from genetic males
What are the three categories of Androgen Insensitivity/Testicular Feminization Syndrome?
- Complete (CAIS; Female phenotype)
- Partial (PAIS; partially masculinized)
- Mild (male phenotype)
What are the symptoms of Androgen Insensitivity/Testicular Feminization Syndrome?
- Testosterone synthesis normal
- No androgen receptor -> no differentiation of Wolffian duct and urogenital sinus
- Accumulated testosterone gets aromatized to E -> secondary female sex characteristics
- AMH/MIS during develpoment is normal and thus Mullerian duct regresses and no uterus
- CAIS and PAIS patients ith female genitalia think like males; gender assignment in the latter could be complex
How does AMH/MIS receptor deficiency cause male pseudohermaphroditism?
A single base pair nonsense mutation in the MIS type II receptor is responsible for canine persistent Mullerian duct syndrome
What is the most common cause of Congenital Adrenal Hyperplasia?
21-hydroxylase deficiency (90-95% of all cases)
What are the sequelae of female pseudohermaphroditism?
- Salt wasters (75%)
- Virilizers (25%)
- Non-classics (<1%)
How does salt wasting affect physiologic conditions?
Salt loss leads to vomiting, weight loss, adrenal crisis, and failure to thrive -> hyponatremic encephalopathy
How does virilization affect physiologic conditions?
Adrenogenital Syndrome (virilization continues after birth, resulting in rapid bone growth and maturation)
How does Adrenogenital Syndrome present in females?
- Pseudohermaphrodites
- Progressive masculinization, hirusitism, epiphyseal closure
- Secondary amenorrhea/oligomenorrhea
How does Adrenogenital Syndrome present in males?
- Appear normal at birth
- Somatic and sexual precocity < 2-3 years
- Little hercules
What is Mayer-Rokitansky-Kuster-Hauser (MRKH) Syndrome?
Causes absence of Rokitansky sequence and a blind vaginal pouch (closing between opening of vagina and cervix)
What cells also make AMH that can cause Mullerian agenesis?
Ovarian granulosa cells, which develops in the ovary postnatally and has a role in folliculogenesis (follicle deviation).
How can ovarian granulosa cells be modified to cause female Mullerian agenesis?
If more is made prenatally, a more potent form is produced, or if the receptor is mutate to be always “on”
What is freemartinism?
When a female heifer shares the placenta with a male bull; placental fluids and cells are exchanged between the two fetuses. Reproductive organs of the male fetus develop earlier than those of a female fetus -> presence of fetal male hormones -> Mullerian Agenesis in Animals
What is Kallman Syndrome?
Failure of GnRH neurons to migrate to hypothalamus; a rare inherited form of hypogonadotropic hypogonadism
Where do the GnRH secreting neurons originate in physiologic conditions?
Olfactory placode and migrate along the olfactory nerves until they reach the forebrain
What else other than GnRH is disabled in Kallman syndrome?
Olfactory fibers
How does Kallman Syndrome occur on a genetic level?
two causal genes (mutations of an x-linked gene that encodes anosmin 1 and an autosomal gene that encodes fibroblast growth factor receptor 1) have been identified so far
What sequelae is caused by Kallman Syndrome?
- Hyposmia or anosmia
- GnRH deficiency (patients remain prepubertal -> eunuchoidism [Having a body like a eunich])
What is the anatomy of the olfactory tract?
Within glomerular layer of the bulb, the axons of olfactory neuons make synapses with dendrites of mitral cells whose axons will form the olfactory tract.
What is KAL protein?
A protein that is normally secreted by mitral cells in olfactory bulb; required for proper interactions with olfactory axons
How is KAL affected in Kallman Syndrome?
Protein is absent -> olfactory axons not interacting properly with dendrites of mitral cells -> failing to form olfactory tract and GnRH neuron migration
What are the signs of Kallman Syndrome?
- Patients with normal growth hormone secretion tend to be normal height for age but lack pubertal growth spurt
- Skeletal development is delayed for chronological age, but continue to grow after age when normal adolescents stop growing
