Sexual determination is initiated by a finely tuned genetic development programme that comprises a complex network of genes. Sexual differentiation of the genitals involves developmental processes that are controlled by the production of sex hormones (e.g. testosterone or oestradiol) and their effects. Changes in the relevant genes (mutations) can impair these developmental processes.

It is assumed that (in addition to genital development) almost all tissues and organs are subject to sex-specific development, which is characterised by different gene expression patterns. It has also been shown that the human brain also develops in a gender-specific manner. In this context, the concept of psychological gender comes into play, which includes gender-specific behaviour, sexual orientation and gender identity.

It can be difficult or impossible to categorise people with variations in gender development as male or female. Medical measures (such as hormone therapies or genital surgery) can be used to clarify the gender or enable assignment to a gender.

DSD includes a variety of diagnoses in different forms. It is often not possible to make a clear genetic diagnosis. The time of diagnosis can be very different, for example directly after birth, in childhood, very often during puberty or only later in adulthood. Depending on the cause, severity and time of diagnosis, a variety of medical and ethical questions arise regarding the further care of those affected, such as the type, extent and aim of treatment. Specialised medical expertise and experience as well as a sensitive approach to those affected are just as important as providing comprehensive information to those affected and their relatives. Careful assessment of all preventive, diagnostic and therapeutic measures, taking into account and weighing up all psychosocial, ethical and legal aspects, is necessary in the care and treatment of people with DSD.

People with variants of sex development are cared for at Ulm University Hospital under the umbrella of the Centre for Rare Diseases (ZSE) in the Specialist Centre for Rare Endocrine Diseases (ZSEE ) by selected experts in line with guidelines as part of an interdisciplinary approach.

Experts from the following departments at Ulm University Hospital work closely together on diagnosis and treatment:

• Department of Paediatrics and Adolescent Medicine, Section of Paediatric Endocrinology and Diabetology
• Department of Internal Medicine I, Section for Endocrinology, Metabolic and Nutritional Sciences
• Department of General and Visceral Surgery, Paediatric Surgery Section
• Department of Urology and Paediatric Urology, Paediatric Urology Section
• Department of Gynaecology and Obstetrics, Paediatric and Adolescent Gynaecology
• Clinic for Child and Adolescent Psychiatry/Psychotherapy
• Institute of Human Genetics
• Central Laboratory for Clinical Chemistry

In 2012, the German Ethics Council published a comprehensive statement on the topic of DSD, which is also reflected in the recommendations of the German Medical Association from 2015. In 2016, an S2K guideline on "Variations in sex development" was published in agreement with patient organisations and medical associations, which takes into account consensus recommendations for the care of people with DSD in the fields of medicine, psychology and self-help.