Androgen insensitivity syndrome is a condition where cells are unable to respond to androgen hormones due to a lack of androgen receptors. It is an X-linked recessive genetic condition, caused by a mutation in the androgen receptor gene on the X chromosome. Extra androgens are converted into oestrogen, resulting in female secondary sexual characteristics. It was previously known as testicular feminisation syndrome.
Patients with androgen insensitivity syndrome are genetically male, with XY sex chromosome. However, the absent response to testosterone and the conversion of additional androgens to oestrogen result in a female phenotype externally. Typical male sexual characteristics do not develop, and patients have normal female external genitalia and breast tissue.
Patients have testes in the abdomen or inguinal canal, and absence of a uterus, upper vagina, cervix, fallopian tubes and ovaries. The female internal organs do not develop because the testes produce anti-Müllerian hormone, which prevents males from developing an upper vagina, uterus, cervix and fallopian tubes.
The insensitivity to androgens also results in a lack of pubic hair, facial hair and male type muscle development. Patients tend to be slightly taller than the female average. Patients are infertile, and there is an increased risk of testicular cancer unless the testes are removed.
This section mainly covers complete androgen insensitivity syndrome. There is also a condition called partial androgen insensitivity syndrome, where there the cells have a partial response to androgens. This presents with more ambiguous signs and symptoms, such as a micropenis or clitoromegaly, bifid scrotum, hypospadias and diminished male characteristics.
Androgen insensitivity syndrome often presents in infancy with inguinal hernias containing testes. Alternatively, it presents at puberty with primary amenorrhoea.
The results of hormone tests are:
- Raised LH
- Normal or raised FSH
- Normal or raised testosterone levels (for a male)
- Raised oestrogen levels (for a male)
Management is coordinated by a specialist MDT, involving paediatrics, gynaecology, urology, endocrinology and clinical psychology. Medical input involves:
- Bilateral orchidectomy (removal of the testes) to avoid testicular tumours
- Oestrogen therapy
- Vaginal dilators or vaginal surgery can be used to create an adequate vaginal length
Generally, patients are raised as female, but this is sensitive and tailored to the individual. They are offered support and counselling to help them understand the condition and promote their psychological, social and sexual wellbeing.
Last updated June 2020