Androgen Insensitivity Syndrome Workup

Updated: Oct 16, 2017
  • Author: Christian A Koch, MD, PhD, FACP, FACE; Chief Editor: Robert P Hoffman, MD  more...
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Workup

Laboratory Studies

The studies described below may be indicated in patients with androgen insensitivity syndrome (AIS).

A karyotype is essential to differentiate an undermasculinized male from a masculinized female. Alternatively, the presence of a Y chromosome can be confirmed by fluorescent in situ hybridization (FISH) probes for either the SRY region of the Y chromosome or a subtelomeric Y chromosome probe. These offer a much quicker turnaround time than conventional karyotypes.

Levels of testosterone and dihydrotestosterone (DHT) establish the presence of normal steroidogenesis. If the testosterone level is low for age, obtain levels of dehydroepiandrosterone (DHEA), androstenedione, and their precursors, 17-hydroxypregnenolone and 17-hydroxyprogesterone. These levels allow identification of errors in the steroid biosynthetic pathways. An elevated ratio of testosterone to DHT indicates a 5-alpha reductase deficiency, a possible differential for patients with partial androgen insensitivity syndrome but usually not for complete androgen insensitivity syndrome. Low levels of testosterone in the absence of evidence of defective steroidogenesis suggest testicular dysgenesis or Leydig cell aplasia/hypoplasia.

Mutation analysis of the androgen receptor gene is now commercially available. It detects upwards of 95% of the mutations for complete androgen insensitivity syndrome and partial androgen insensitivity syndrome. The analysis is performed on DNA obtained from buccal swabs. However, the testing is slow (about 6 wk for results) and expensive (not covered by some insurance companies).

For patients with Kennedy disease, an elevated testosterone level can be found in approximately 70% of cases. More than 40 CAG tandem repeats in exon 1 of the AR are diagnostic. [13]

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Imaging Studies

A pelvic ultrasound examination is frequently useful. Identification of any müllerian structures, such as uterus or fallopian tubes, is inconsistent with a diagnosis of complete androgen insensitivity syndrome or partial androgen insensitivity syndrome.

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Histologic Findings

Histologic examination of the testes in patients with complete androgen insensitivity syndrome or partial androgen insensitivity syndrome should show fairly normal testicular structure, although the numbers of spermatogonia and/or sperm may be reduced markedly in postpubertal patients.

Given current management recommendations, a histologic examination may be impossible to perform until the patient is in late adolescence or early adulthood.

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