The topic of intersexuality is not new either to the public or to scientists, but the discussion of all parameters and issues associated with the subject is relatively new. And much new material is constantly being added to or amending the old.


The general public has long been familiar with the common term hermaphrodite. Those so designated were often associated in the public mind with circus sideshow exhibits of so-called half-man and half-woman persons. In truth there are extremely few such people but there are, indeed, many individuals that are born naturally with characteristics of both typical males and females. And the conditions are, while not common, by no means rare (Blackless, Charuvastra et al. 2000).

While many animal species are known to be hermaphroditic, for humans the term hermaphrodite is no longer considered polite or politically correct. Those with these male-female combinations of characteristics prefer to be known as intersexed or persons with intersex conditions. Basically this refers to the fact that their bodies contain features that are usually seen separately in both men and women. These persons might, for instance have gonads consisting of one ovary and one testis or gonads that are combined ovatestes. Or they might have chromosome combinations that are atypical. Humans commonly have twenty-three sets of chromosomes (46 chromosomes). Twenty-two pairs (44) of chromosomes are called autosomes. The other pair of two chromosomes is called the sex chromosomes. Males usually have one X sex chromosome and one Y sex chromosome. Typically females have two sex chromosomes that are both Xs. Occasionally, however, individuals are born with sex chromosomes that are of different combinations. This involves one type of individuals that are intersexed because of genetic variation. The most common different Intersex combination of sex chromosomes is XXY and is called a typical Klinefelter syndrome. Other combinations, such as XXXY, XXXXY and XYY also exist. These are called Klinefelter variants. An individual might also be born with a chromosome missing and thus have 22 sets of autosomes and an XO combination of sex chromosomes where the O indicates a sex chromosome (originally either an X or Y) has been lost. These persons are said to have a Turner syndrome intersex condition.

In general society, when a baby is born, one of the first questions asked is this: “Is it a boy or a girl”, and the determination is made quickly and simply. If the genital appendage looks like a penis, the baby is considered a male and is to be raised as a boy. A baby born without a penis is considered a female and raised as a girl. But nature is not that simple. Babies are born that do not have a penis and yet are males based on other characteristics, and babies are born with genitals that look like a penis but are, in reality, females based on other factors. Individuals with a Y chromosome usually have a phallus that is penis shaped and so are dubbed as male when they are born. Those without a Y chromosome (such as those with XX chromosomes or an XO (Turner) set of sex chromosomes) do not have a penis-like phallus and are seen as female. To complicate matters further: Babies, perhaps as many as one in 2 to 4 thousand, are born with genitals that are not easily categorized as male or female. There is no clear penis or vaginal entrance. These genitals are considered ambiguous so a designation of male or female is not immediately apparent. These children are the most commonly known intersexed persons; at birth they have genitals that combine obvious features of male and female. There are other types of intersex persons, perhaps the majority, in which the designation is not known until puberty or later.

Obviously the definitions of male and female are at issue. Biologically there have been several ways to define these terms. These definitions have not always been consistent, and still not everyone agrees on which characteristics or features should be given prominence. The primary biological or medical sexual characteristic to distinguish male from female had been either the gonads (does the individual possess testicles or ovaries) or the chromosomes (are the sex chromosome combination XY or XX). But, over the years, as exemplified above, it became clear that many different combinations existed. To further complicate the matter, persons with these different biological features might live as men or women regardless of whether they were assigned as boy or girl. Here it becomes obvious that male and female are used as biological designations while boy and girl and man and woman are seen as social descriptions. Males could live as girls or women and females could live as boys or men.

This potential of how persons might live and identify has obvious social and sociopolitical ramifications. The general public wants and expects things to be simple and obvious and consistent. They expect males to live as men and have a visible penis and other masculine features. In a similar way they want females to have an obvious vagina and breasts and live as women. With persons having intersex conditions this might or might not be so. This ability to mix and match biological and social features varies in different cultures; in some it is accepted and legal to do so and in some it is not accepted and considered illegal. Some religions feel strongly about this and others less so. And intersexed persons themselves often wish to have their own option on how to be addressed and considered; either as man or woman or intersex. Not all factions of society accept this.

In a well-meaning attempt to clarify this matter, a group of physicians and others met in 2006 and agreed to call intersex conditions Disorders of Sex Development or DSD (Hughes, Houk et al. 2006) thus getting away from the term hermaphrodite and intersex altogether. Many physicians who have to deal with some of the aspects of intersexual conditions thought this a wise solution since the label Disorder put these conditions under the banner of medical issues with which they deal. However, this terminology did not please everyone. Many intersex persons did not want to be labeled as having a disorder. I and other colleagues agree and think to consider persons with these conditions as disordered is not only stigmatizing but wrong since they are, in most cases, healthy, undistinguishable from their peers and not in need of medical attention (Beh and Diamond 2007; Tamar-Mattis and Diamond 2007; Diamond and Beh 2008) . Indeed, I’ve not met any parents who are happy to learn that their child is disordered. The terminology that is used in this article is male or female depending upon the gonads or chromosomes the individual possesses; usually they are in concert. When I use the abbreviation DSD it refers to Differences of Sex Development. If a male prefers to see himself as a woman I use the female pronoun to refer to her. Likewise, if a female saw herself as a man I refer to him with male pronouns. It is the most courteous thing to do. This reflects on the issue of social sex - usually referred to as gender - as touched on above.

Most commonly males are considered to have two testicles as gonads and females are considered to have two ovaries. The gonads of the male produce sperm and those of the female produce ova (eggs). The sperm are released into bilateral ducts (Latin singular: ductus deferens) that take sperm and accompanying fluids to the urethra within the penis. The ova are released into bilateral oviducts (Fallopian tubes) that lead to the uterus. Males have an extended phallus called a penis while females have a phallus called a clitoris. These and other sex differences are shown in Table 1. For comparison examples are given where male and female intersex variations are merged. While this brief paragraph describes factors associated with reproduction, many intersex conditions involve infertility. It is a feature of the syndrome that is often most disturbing to the individual. Often the gonads do not function to produce viable ova or sperm.

The most common intersex condition is called Congenital Adrenal Hyperplasia (CAH). CAH can occur in otherwise typical males or females and is due to an overproduction of androgens by the fetus or mother’s adrenal glands. This can occur during pregnancy so the female infant is born with a slightly enlarged clitoris/phallus or her genitals might be masculinized enough to be ambiguous. Or she might look as if she has a penis and her labia might be fused to appear as a scrotum. In cases where the condition is such that the infant would lose needed body salts it is one of the few intersex conditions that require serious and immediate medical attention. (See Nieman 2010 for more details about CAH.) CAH is one of the few Intersex conditions where the individual maintains reproductive capacity.

CAH is due to an enzymatic deficiency where, for more than 90 percent of cases, the normal conversion of hormones (17-hydroxyprogesterone to 11-deoxycortisol) does not occur and the body-needed cortisol is not produced and must be provided. This conversion of hormones is mediated by an enzyme (21-hydroxylase) that is deficient. But other hormones can block the normal formation of cortisol and lead to CAH. There are many other Intersex conditions caused by other enzyme deficiencies. Two common ones are simply called by an abbreviation of the enzyme involved, i.e., 5-alpha deficiency (Wilson 2009) and 17-beta dehydrogenase deficiency (Geissler, Davis et al. 1994). Both of these conditions give rise to male infants born looking like females; they appear without penises. In these conditions, the deficient enzymes develop with maturity and allow for increased masculinization. Usually, with puberty, the masculinization has proceeded to the extent that these persons, although raised as girls switch to live as boys and then men (Imperato-McGinley, Peterson et al. 1979; Imperato-McGinley, Peterson et al. 1979; Imperato-McGinley, Miller et al. 1991).

Table 1. Comparison of Male, Female and Intersex

  Male Female Intersex Example1
Chromosomes XY XX XXY
Gonads Testicles Ovaries Ovatestes
Phallus Penis Clitoris Ambiguous
Ducts Ductus Deferens Oviducts  
  Scrotum Labia Ambiguous
Breasts Flat chest Fatty w/mammary glandular tissue Flat, Full or Ambiguous
Gametes Sperm Ova Generally Infertile

1 This is only one type of intersex combination. There may be many others.

Categories of intersex conditions

Intersex conditions can result from three main fundamental processes; genetic, enzymatic-hormonal and receptor based. As mentioned above the most typical genetic causes of intersex involve chromosomal variation. Usually this variation extends throughout the whole body. Each body cell contains a like chromosomal complement. A less frequently seen variety is where there is variation that shows differences in separate areas of the body. This is called mosaicism. In such cases there exists a mixture of cells so that one part of the body might be XX in character while XY in another. One part of such a body might contain a testis while another contains a uterus. In extremely rare cases a person might essentially be a male on one side of the body and a female on the other. This is called a chimeric condition. (Imagine a potential set of eggs that might have gone on to produce twins instead combining to produce one person.)

Another set of etiological causes of intersex conditions result from varieties of enzymatic-hormonal interactions. These were mentioned above where CAH was the main example. Other examples were the 5-alpha and 17-beta variety.

A third variety of intersex conditions are caused by a normal receptor absence. Receptors are molecules on the surface of cells that combine with different biochemical factors to allow for their normal biochemical operation. In some cases the receptors needed for different hormonal activities are absent or do not function properly. Such a type of intersex condition is called the Androgen Insensitivity Syndrome (AIS) of which there are two types; a complete variety (cAIS) and a partial type (pAIS). Since androgens are needed for the development of maleness in structures as well as behavior the syndromes are considered among other androgen deficiency syndromes. With complete AIS, since their body cannot respond to the hormones needed for male structural sexual differentiation, these persons develop looking as females despite having testes that produce adequate amounts of the androgen testosterone. At puberty breast development is common because much of the androgen is converted to feminizing estrogens. With the partial variety of AIS many phenotypes occur. Some persons with pAIS have a small penile phallus and develop breasts while others do not. Most persons with this condition live as women but others live as men. Many androgynous persons have occult and undiagnosed conditions of pAIS. A subset of such individuals will be raised as males but go on to live as women.

Some history of the management of intersexuality

Prior to the 1950s, intersexuality and its various manifestations were poorly understood and considered a condition of shame and to be hidden. Medical treatment was minimal and, when offered, based on obvious symptoms rather than a clear diagnosis of etiology. Individuals, so affected, were generally assigned a gender based on the appearance of their genitals; if they looked more penis-like at birth the child was assigned as a boy and if the genitals appeared more like a girl’s the child was assigned as such. Social and cultural conditions were such that persons unhappy with the assigned sex were usually forced to maintain the gender of assignment despite contradictions in feelings and other aspects of sexual life. Complications that might have developed such as being sexually attracted to those that might be socially considered inappropriate or discomfort in living according to social expectations considered distasteful were seen as aspects of life that were to be endured.

Since most persons with these identified intersex conditions stayed in their sex of birth assignment and did not switch their gender identity, it led the investigator John Money to mistakenly believe and propose that individuals are psychosexually neutral at birth and that it mattered not if they were raised as boys or girls (Money, Hampson et al. 1955; Money 1963). Despite the fact that this theory was extracted from cases of intersex it was proposed to hold as well for typical individuals (see Diamond 1999). Regardless of how they were biologically, it was believed that intersex children would accept the gender assigned to them at birth. Many of such children, noted at birth due to their ambiguous genitalia, were then often subjected to surgery to normalize their genitalia. This was in the belief that as adults they would thank the surgeons for relieving them of potential embarrassment. It is now known that such treatment was well meaning but wrong.

For the most part, when choosing surgical treatment, physicians opted for a believed optimum female form because it is easier to fashion female genitalia than male. This held true for males as well as females. Males would be reassigned as girls and females would have any enlarged clitoris removed or reduced in size. And then, relying on a nurture-based theory of gender identity, physicians advised parents to accept their surgically altered infant and to raise the child in a manner consistent with the child’s surgically altered genitalia. This was to hold without regard to any gender identity that might have naturally developed (Kessler 1990; Kessler 1997). The same advice has been given when a male infant’s penis has been severely mutilated by trauma or is considered significantly small. Clinicians had assured parents that the surgical potential for normal-looking genitalia should dictate the child’s gender and that any innate gender propensity of the child can be changed by careful upbringing.

Despite a paucity of confirming evidence, medical literature since the 1970s, had promoted this treatment until the end of the twentieth century. The medical literature relied on a body of published reports which themselves were initially predicated on studies of intersex individuals and most significantly, one infant’s incredible case which was widely reported in medical, psychiatric and popular literature (Money, Hampson et al. 1955; Money 1963). In 1997, the medical community was reacquainted with that infant who had been reported as long lost to follow-up (Diamond and Sigmundson 1997). Only then did the medical community discover that the outcome of this single case (now known as that of John/Joan) was not as first reported. The foundation on which the old treatment rested began to crumble. It is now known that infants are not psychosexually neutral at birth but are, instead, biased as males or females (or intersexed) at birth and there is no way, until the child is old enough to express his or her own feelings, to know if the preference is to live as a boy or girl, man or woman, or in some manner of their own choosing (Diamond 2006; Diamond 2009). Until then it is best to do no surgery, encourage the parents to love the child as it is, and raise it as a boy or girl based on the best bio-medical information available.

Fortunately, at least in the USA (Diamond, Burns et al. 2005) and among the most enlightened areas of the world, practices for the management of intersex cases are changing and cases of cosmetic infant surgeries are becoming less common. Physicians and parents are becoming more accepting of this and are willing to wait and see how the child itself prefers to live. Decisions as to how to raise the child with ambiguous genitalia are based, not on whim or guesswork, but on the best diagnostic evaluation available. Parents are also increasingly aware that their children might make decisions as to gender and partner choices that were not predictable at birth. Fortunately there now exist many support groups both available to parents of intersexed children and support groups for persons of many different intersex varieties.

Intersexuality among non-human species

In plants and non-human animals intersexuality is quite common. While there are plants that have only flowers with male or female parts there are many with flowers that have both male and female parts. And adding to this are plants with flowers that have all three types of flowers; male, female and combined. Plants that have flowers with both male and female gametes are called perfect because they can pollinate themselves requiring neither wind nor insects. (Despite mythology and fantasy this cannot happen with humans.) Peppers and tomatoes are examples of plants with flowers considered perfect.

In animals, particularly fish, there are three types of intersexuality and in these cases the term hermaphrodite is still considered correct. In the first variety there are simultaneous hermaphrodites where individuals can copulate and reproduce both as males and females simultaneously. Hamlets are one such species type of reef fish where individuals can mate taking turns as either male or female.

The second and third varieties, also quite common among reef fishes, are protoandrous hermaphrodites and protogynous hermaphrodites. These are similar except that for those species that are protoandrous the organism starts off as male and changes to female. For those species that are protogynous the organism starts life as a female. The stimulus for change might be visual, pheromonal or tactual.

Mammals, other than humans, are also known to exhibit intersexuality. Perhaps the most commonly known examples are those in farm animals such as pigs and cattle (often called Freemartin) but non-domesticated animals also have been reported.


Many people make a clear and sometime very vocal distinction between intersexuality and transsexuality. Most opposition to linking these two concepts or categories come from those intersexed individuals who think their own situation in the public eye is somehow diminished by the association. This is regrettable. Both of these sexual minorities are stigmatized in society and I think they not only should rather be allies in their fight against discrimination, but also, actually think they have things in common. I maintain that transsexuality is a form of intersex. I conclude this derived from my own clinical experiences, my own experimental research, and knowledge of the research of others. I accept that my thoughts on this matter are a minority view among colleagues and fellow scientists.

I believe that transsexuals are intersexed in their brains as others are or might be more obviously so in their gonads, genitals, hormonal character, receptor, enzymatic or chromosomal constitution. And it is this brain intersexuality that biases the person to assert his or her gender identity.

As one can vary on a Kinsey scale from 0 to 6, and can fluctuate during one’s life so too can one vary from 0 to 6 on the Benjamin scale (Benjamin 1966) demonstrating different degrees of a trans identity. This can be manifested from occasional cross-dressing to a full-time transsexuality where a person desires to live full-time in a mode different from the way he or she was born and raised. And this gender identity can fluctuate from mild to intense during different times in one’s life and in reaction to a variety of life experiences. These reflect differences, not disorders, of identity. While some persons are seriously impaired by these conflicts of identity and societies views of propriety and might need and desire help in resolution, others have managed to come to terms with their inherent biases and the negative social demands they encounter and see no need for counseling or therapy. While some may be seriously psychically disturbed and require or desire counseling or medical assistance, I don’t see persons with trans variations as mentally ill based solely on their manifestation of a trans condition. And certainly there are examples enough where obviously intersexed persons reared in one gender have decided later in life to switch to the other.

There are of course, also persons with strong transsexual feelings that do not transition just as there are those obviously intersexed that elect not to change from existing conditions that they find distasteful or uncomfortable. They do so to solve other of their life problems with which they have to contend, for example: Will the change mean the loss of family, religion, job, children, etc. Because persons are willing to confront the social conflicts and difficulties involved in living a trans or intersex existence, I see them as only different in expression and character from others that do so by expressing major open societal differences in sexual orientation, religion or other feature of their inherent physical or psychological biases. I think society should understand this characterization. I also think professional therapists, via the Diagnostic and Statistical Manual (DSM) of the American Psychiatric Association should reflect this possibility and potential.

Support groups for intersex and transsexual persons

There are many groups available to assist those with intersex and transsexual conditions. For a list of the most important of these groups, click here.
For a free online course on intersexuality, click here.



Beh, H. G. and M. Diamond (2000). "An emerging ethical and medical dilemma: Should physicians perform sex assignment surgery on infants with ambiguous genitalia?." Michigan Journal of Gender and Law 7(1 (Winter)): 1-63.

Beh, H. G. and M. Diamond (2007). "Managing Variations in Sex Development." Journal of Pediatric Endocrinology & Metabolism, 20(4): 552-553.

Benjamin, H. (1966). "The transsexual phenomenon: Appendix D." International Journal of Transsexuality (IJT) Retrieved 6 August 2003, 2003.

Blackless, M., A. Charuvastra, et al. (2000). "How Sexually Dimorphic Are We." American Journal of Human Biology 12: 151-166.

Diamond, D. A., J. P. Burns, et al. (2005). "Assignments for Newborns with Ambiguous Genitalia and Exposure to Fetal Testosterone: Platitudes and Practices of Pediatric Urologists. ." Journal of Pediatrics 148: 145-149.

Diamond, M. (1999). "Pediatric management of ambiguous and traumatized genitalia." The Journal of Urology 162: 1021-1028.

Diamond, M. (2006). "Biased-interaction theory of psychosexual development: "How does one know if one is male or female?"." Sex Roles 55(9-10): 589-600.

Diamond, M. (2009 ). "Clinical Implications of the Organizational and Activational Effects of Hormones " Hormones and Behavior 55(5): 621-632.

Diamond, M. and H. G. Beh (2008). "Changes In Management Of Children With Differences Of Sex Development." Nature Clinical Practice: Endocrinology & Metabolism 4(1): 4-5.

Diamond, M. and H. K. Sigmundson (1997). "Sex Reassignment at Birth: Long Term Review and Clinical Implications." Archives of Pediatrics and Adolescent Medicine 151(March): 298-304.

Geissler, W. M., D. L. Davis, et al. (1994). "Male pseudohermaphroditism caused by mutations of testicular 17−hydroxysteroid dehydrogenase 3." Nature Genetics 7: 34 - 39.

Hughes, I. A., C. Houk, et al. (2006). "Consensus statement on management of intersex disorders. ." Archives of Disease in Childhood 91(7): 554-563. .

Imperato-McGinley, J., M. Miller, et al. (1991). "A cluster of male pseudohermaphrodites with 5 alpha-reductase deficiency in Papua New Guinea." Clin Endocrinol (Oxf) 34(4): 293-298.

Imperato-McGinley, J., R. E. Peterson, et al. (1979). "Male pseudohermaphroditism secondary to 5 alpha-reductase deficiency--a model for the role of androgens in both the development of the male phenotype and the evolution of a male gender identity." Journal of Steroid Biochemistry and Molecular Biology 11(1B): 637-645.

Imperato-McGinley, J., R. E. Peterson, et al. (1979). "Male pseudohermaphroditism secondary to 17B-hydroxysteroid dehydrogenase deficiency: Gender role change with puberty." Journal of Clinical Endocrinology and Metabolism 49: 391-395.

Kessler, S. (1997). Creating good-looking genitals in the service of gender. A Queer World. M. Duberman. New York, N.Y.U. Press.

Kessler, S. J. (1990). "The medical construction of gender: case management of intersexed infants." Signs: Journal of Women in Culture and Society 16(11): 3-26.

Money, J. (1963). "Cytogenetic and Psychosexual incongruities with a note on space form Blindness." American Journal of Psychiatry 119: 820-827.

Money, J., J. G. Hampson, et al. (1955). "An examination of some basic sexual concepts: the evidence of human hermaphroditism." Bulletin of the Johns Hopkins Hospital 97: 301-319.

Nieman, L. K. (2010) "Diagnosis and treatment of nonclassic (late-onset) congenital adrenal hyperplasia due to 21-hydroxylase deficiency." UpToDate.

Tamar-Mattis, A. and M. Diamond (2007 ). "Managing variation in sex development." Journal of Pediatric Endocrinology & Metabolism 20 (4 ): 552-553.

Wilson, B. E. (2009) "5-Alpha-Reductase Deficiency." eMedicine from WebMD.


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