Who are intersex persons?

Intersex is an umbrella term that includes all congenital (i.e., present from birth) variations of sex characteristics that do not fit into the typical notions of what is considered a male or a female body. These variations may involve sex chromosomes, sex hormones, external genitalia, or internal parts of the reproductive system. It is noteworthy that the terminological debate regarding intersex is still heated, with the direct involvement of users, physicians, researchers, and activists. Initially, intersex people were also called “hermaphrodites”, a term that nowadays is considered misleading, stigmatizing and scientifically incorrect. In medical circles, at the 2005 International Consensus Conference on the Management of Intersex Conditions, the expression “Disorders of Sex Development” (DSDs) was coined to refer to “congenital conditions in which chromosomal, gonadal or anatomical sex development is atypical.” This expression has been strongly criticized by intersex movements and part of the scientific community because it implies that the intersex condition is a pathological and/or disturbing condition to be “normalised” by medical procedures. Thus, the expression “Disorders of Sex Development” has been replaced by “Differences of Sex Development” (DSDs) and more recently by “Variations of Sex Characteristics” (VSCs). The latter expression, “Variations of Sex Characteristics”, is increasingly used in the social sciences, intersex movements, and international organizations, for example Council of Europe, institutional  web sites (e.g., United Kingdom, Iceland and New Zealand) but it is sparsely found in the biomedical literature, where the terms disorders of, or differences of, sex development prevail.

In the documents of this website, we have chosen to use the expression "Variations of Sex Characteristics" (VSCs) and "Differences of Sex Development" (DSDs) with a view to the use of an inclusive language but also capable of reaching the widest number of healthcare providers and, more generally, of citizens. 

VSCs/DSDs can be determined by genetic factors that can lead, at least in some cases, to exposure to unaccustomed levels of sex hormones or to an atypical response to sex hormones by the body before birth (prenatal) or immediately after birth (perinatal). Although we speak of VSCs/DSDs to indicate a condition one is born with, this may not necessarily be recognizable right away. In some cases, intersex traits are visible at birth –e.g., the presence of genitalia that are not recognized as typically male or female (atypical genitalia)– while in other cases they become evident only with the onset of puberty. There are also conditions that are not externally visible, and often remain unrecognized during the person's lifetime.

In general, VSCs/DSDs do not impair the health and survival of a person. Only some VSCs/DSDs can be associated with potentially life-threatening medical problems (e.g., congenital adrenal hyperplasia with salt loss).

The frequency of VSCs/DSDs in the general population may vary between different VSCs/DSDs and also between different countries and ethnic groups. To date, there is no exact estimate of the intersex population. International scientific literature indicates percentages generally ranging from 0.018% to 1.7%. Specifically, some VSCs/DSDs may be rarer (e.g., complete insensitivity to androgens occurs in about 1 in 100,000 births with 46,XY karyotype, and congenital adrenal hyperplasia in the classical form occurs in about 1 in 15,000 births with 46,XX karyotype) compared to others (e.g., Klinefelter syndrome occurs in about 1 case in 500-1,000 born with karyotype 46,XY).

Bibliography
Background Note on Human Rights Violations against Intersex People  
Blackless M et al. How sexually dimorphic are we? Review and synthesis. [Abstract]. American Journal of Human Biology. 2000 Mar;12(2):151-166
Crocetti D et al. Towards an agency-based model of intersex, variations of sex characteristics (VSC) and DSD/dsd health. Culture, Health & Sexuality. 2021 Apr;23(4):500-515
Hughes IA et al. Consensus statement on management of intersex disorders. Archives Disease in Childhood. 2006 Jul;91(7):554-63
Hughes IA et al. Consequences of the ESPE/LWPES guidelines for diagnosis and treatment of disorders of sex development  [Abstract]. Best Practice & Research Clinical Endocrinology Metabolism. 2007 Sep;21(3):351-65
Mongan NP et al. Androgen insensitivity syndrome [Abstract]. Best Practice & Research Clinical Endocrinology Metabolism. 2015 Aug; 29(4):569-80 
Sax L. How common is intersex? A response to Anne Fausto-Sterling [Abstract]. Journal of sex research. 2002 Aug; 39(3):174-8
Therrell BL. Newborn screening for congenital adrenal hyperplasia [Abstract]. Endocrinology and Metabolism Clinics North America. 2001 Mar;30(1):15-30