What is androgen receptor resistance?
An androgen receptor resistance is a rare congenital disorder in which body cells respond only partially or not at all to male sex hormones such as testosterone or dihydrotestosterone (DHT).
It is caused by changes (mutations) in the androgen receptor, which mediates the effects of these hormones in the cells.
Although testosterone levels may be normal or even elevated, the hormonal effect may be significantly reduced. Symptoms are therefore not caused by a lack of testosterone, but by the target cells' reduced sensitivity to androgens.
Depending on its severity, androgen receptor resistance can lead to very different clinical presentations.
How does androgen receptor resistance develop?
For testosterone and DHT to exert their effects, they must bind to the androgen receptor in the target cells.
In androgen receptor resistance, the function of this receptor is impaired. As a result, the hormones can only exert their effects partially or not at all, even though they are present in sufficient quantities.
The disorder is usually caused by changes in the AR gene, which is located on the X chromosome. This is why clinically relevant androgen receptor resistance affects almost exclusively people with a male chromosome set (46,XY).
What forms of androgen receptor resistance are there?
Depending on the extent to which the androgen receptor's function is impaired, different forms are distinguished.
Complete androgen receptor resistance (CAIS)
In the complete form, body cells practically do not respond to androgens. Affected individuals have a male chromosome set (46,XY) but develop female external genitalia.
Partial androgen receptor resistance (PAIS)
In the partial form, there is still some sensitivity to androgens. The presentation can vary widely, ranging from slightly impaired masculinization to pronounced disorders of sexual development.
Mild androgen receptor resistance (MAIS)
In the mild form, external male genitalia are usually normally developed. Symptoms may include, for example, reduced fertility, gynecomastia, or a reduced effect of testosterone.
What symptoms may occur?
Symptoms depend on the severity of the androgen receptor resistance.
Possible symptoms include:
- absent or incomplete male puberty development
- reduced beard and body hair growth
- gynecomastia
- reduced fertility or infertility
- small testes
- reduced muscle development
- reduced effect of testosterone despite normal hormone levels
In complete forms, abnormalities in sexual development may be evident at birth.
How is androgen receptor resistance diagnosed?
The diagnosis is based on a combination of clinical findings, hormonal testing, and genetic testing.
Typically, the following laboratory values are determined, among others:
- Total testosterone
- Free testosterone
- LH
- FSH
- Estradiol
Normal or elevated testosterone levels are often accompanied by elevated LH, as the body attempts to compensate for the reduced hormonal effect.
The definitive diagnosis is usually made by demonstrating a mutation in the AR gene.
How does androgen receptor resistance differ from a testosterone deficiency?
Androgen receptor resistance and testosterone deficiency can cause similar symptoms, but they are fundamentally different.
In testosterone deficiency, the body produces too little testosterone.
In androgen receptor resistance, however, there is sufficient or even excess testosterone, but the target cells cannot respond appropriately.
Therefore, determining hormone levels alone is not always sufficient. For diagnosis, symptoms, laboratory findings, and, if necessary, genetic tests must be assessed together. You can read about what a classic testosterone deficiency manifests as and how it is treated in our article Testosterone deficiency in men: causes, symptoms and solutions.
How is androgen receptor resistance treated?
Treatment depends on the severity of the disorder and individual symptoms.
Depending on the form, various measures may be necessary, for example:
- hormone therapy
- surgical procedures for disorders of sexual development
- treatment of gynecomastia
- reproductive medicine consultation for those wishing to have children
- genetic counseling
As it is a rare disorder, care is often provided in specialized endocrinology centers.
What role does androgen receptor resistance play in everyday life?
Classic androgen receptor resistance is a rare genetic disorder and differs significantly from the common causes of testosterone deficiency.
In addition, research is investigating whether natural genetic differences in the androgen receptor, such as so-called CAG repeat polymorphisms, affect individual sensitivity to testosterone. However, their clinical significance in everyday life has not yet been conclusively established, and they currently play no established role in routine diagnostics.
Conclusion
Androgen receptor resistance is a rare congenital disorder in which body cells respond only partially to testosterone and DHT. It is caused by changes in the androgen receptor, which reduce the hormonal effect despite normal or elevated testosterone levels.
In addition to hormonal testing, diagnosis often requires genetic testing. Treatment depends on the severity of the disorder and individual symptoms.