Disruptions in androgen signaling

Disruptions in androgen signaling during development can lead to reduced expression of the male phenotype:

  1. Gonadal dysgenesis (impaired testicular development).
  2. Leydig cell hypoplasia (reduced testosterone production).
  3. Testosterone biosynthesis defects.
  4. 5-alpha reductase deficiency.
  5. Androgen receptor defects.

In androgen receptor defects, the internal genitalia are always male, but the external phenotype can range from normal male to completely female, with intermediate stages.

Phenotypic Classification of Virilization Disorders

Type

Phenotype

Features/Function

1

Male

Impaired spermatogenesis or virilization in puberty.

2

Predominantly male

Isolated hypospadias, micropenis, higher-grade hypospadias.

3

Ambiguous

Clitoris-like micropenis, labia-like scrotum, perineal hypospadias.

4

Predominantly female

Clitoral hypertrophy, labial fusion, blind-ending vagina.

5

Female

No virilization prepubertally; virilization or feminization during puberty.

Types of Androgen Insensitivity

  1. Mild Androgen Insensitivity Syndrome (MAIS):
    • Minimal symptoms such as reduced body hair or gynecomastia. Often noticed due to infertility.
  2. Partial Androgen Insensitivity Syndrome (PAIS):
    • Also known as Reifenstein Syndrome; causes a range of ambiguous genitalia.
  3. Complete Androgen Insensitivity Syndrome (CAIS):
    • Also called testicular feminization syndrome. These individuals have a 46,XY karyotype and high testosterone levels but appear phenotypically female with normal breast development

Diagnosis

Diagnosis

  1. Before Puberty:
    • Perform an hCG stimulation test. If testosterone remains below 10 nmol/L, multiple stimulations are required.
    • Measure the testosterone/DHT ratio; a ratio >16 suggests a 5-alpha reductase defect or androgen receptor defect.
  2. After Puberty:
    • Typical findings include high testosterone and LH levels.
    • Testosterone is converted to estradiol, leading to gynecomastia in male patients. In phenotypically female patients, breast development occurs normally (testicular feminization).
  3. Genetic Testing:
    • Identify mutations in the androgen receptor gene or 5-alpha reductase gene (SRD5A2).

5-Alpha Reductase Deficiency

  • Patients have a 46,XY karyotype with normal to high testosterone secretion.
  • Incomplete conversion of testosterone to DHT results in a female phenotype at birth.
  • Virilization occurs during puberty due to testosterone action.
  • Diagnosis involves measuring low DHT concentrations with a normal testosterone level and an elevated testosterone/DHT ratio (>16).

Treatment

  1. For CAIS (Complete Androgen Insensitivity):
    • If assigned female, gonads should be removed before puberty to prevent unwanted virilization.
  2. For PAIS:
    • Management depends on the severity of virilization and the assigned gender.
  3. For MAIS:
    • Minimal treatment is needed; symptoms like gynecomastia can be addressed surgically.

Differential Diagnosis of Intersexuality

Diagnostic Test

Conclusion

Family history, maternal virilization

Genetic factors, exogenous influences.

Physical exam (gonads, vagina)

Presence of internal/external structures determines cause.

Chromosome analysis

Detects gonadal dysgenesis or hermaphroditism.

Hormonal tests (LH, FSH, testosterone)

Androgen synthesis or receptor defects.

hCG test

Assesses testosterone production and conversion.

Molecular genetics

Identifies mutations in androgen receptor or 5-alpha reductase genes.

Androgen resistance syndromes, including CAIS, PAIS, and MAIS, are caused by mutations in the androgen receptor gene. The phenotypic spectrum ranges from normal male appearance to complete feminization in individuals with a 46,XY karyotype. Diagnosis involves hormonal testing, genetic analysis, and clinical evaluation.

For patients assigned to the female gender, timely removal of the gonads is essential to prevent unwanted virilization. Accurate diagnosis and management ensure proper gender assignment and treatment planning.