For anybody looking for a detailed explanation of intersex conditions, I apologise. This isn't the lens to cover that in detail. I have written one specialist lens about Klinefelter's Syndrome so far, and am more.
Contents at a Glance
Physical Indicators
Secondary Sexual Characteristics
Secondary sexual characteristics are a very weak way of determining gender. If a woman takes testosterone her voice will break and she will grow a beard and if a man takes estrogen (predominently estradiol) he will grow breasts. For this, and other reasons, secondary sexual characteristics like breards and breasts, while what people notice first, are not reliable indicators of gender.
Primary Sexual Characteristics
Hermaphrodism & Physical Intersex Conditions
Hormones and Gender
Testosterone and Estradiol (Estrogen)
Testosterone
The video gives only a very basic introduction, for further information about the main male sex hormone testosterone, the Wikipedia article is a good place to start.It is produced in a number of ways, but in men the main factory for testosterone is the testes.
Testosterone is a steroid hormone from the androgen group. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands. It is the principal male sex hormone and an anabolic steroid. Testosterone is evolutionarily conserved through most vertebrates, although fish make a slightly different form called 11-ketotestosterone.
In men, testosterone plays a key role in health and well-being as well as preventing osteoporosis. On average, an adult human male body produces about forty to sixty times more testosterone than an adult human female body, but females are, from a behavioral perspective (rather than from an anatomical or biological perspective), more sensitive to the hormone. However, the overall ranges for male and female are very wide, such that the ranges actually overlap at the low end and high end respectively.
Estradiol
There are many estrogens in women (just as testosterone is only one androgen). The primary estrogen between menarche and menopause is estradiol. After menopause, it is usually estrone. (After menopause estrogen, often estradiol, is the key ingredient in hormone replacement therapy - HRT, prescribed to smooth out the hormonal changes) You can read more about estradiol in this Wikipedia article. The main - but by no means exclusive - source of production in women is the ovaries.
Estradiol (E2 or 17?-estradiol) (also oestradiol) is a sex hormone. Estradiol is the predominant sex hormone present in females; however, it is present in males, albeit at lower levels, as well. It represents the major estrogen in humans. Estradiol has not only a critical impact on reproductive and sexual functioning, but also affects other organs including the bones.
Aromotase Converts Testosterone to Estradiol
Although estradiol is the main female sex hormone, it is also present in men. Testosterone can be converted to estradiol by the action of the enzyme aromtase in a process known as aromatization. Estradiol is produced in men by testes. Small quantities are produced in both sexes in a wide range of tissues and glands.
Estradiol is therefore present in both men and women. Similarly testosterone is made by the body in a variety of ways, not just in the testes. Women's testosterone levels usually peak around the middle of the menstrual cycle, increasing libido when a woman is most likely to be fertile.
Neither sex hormone is unique to men or women.
Aromatase is an enzyme that is responsible for a key step in the biosynthesis of estrogens. Because estrogens also promote certain cancers and other diseases, aromatase inhibitors are frequently used to treat those diseases.
Steroids are composed of four fused rings (labeled A, B, C, and D in the figure below). Aromatase transforms the left-hand ring (the A-ring) of steroids to an aromatic state (hence the name) through oxidation and subsequent elimination of a methyl group.
Category: Image - :Testosterone_estradiol_conversion.png|thumb|center|400px|Aromatase converts testosterone to estradiol
Aromatase is a member of the cytochrome P450 superfamily (), whose function is to aromatize androgens, producing estrogens. As such, it is an important factor in sexual development.
Genetics and Gender
Genetics Primer
It's common to refer to males as genetically XY and females as XX. This refers to variation between the two genders in chromosome 23 of human DNA. Before we look at variations with the basics of genetic sex determination, if you aren't familar, or your knowledge is rusty, then you might want to use one of these genetics primers as a refresher. (If you are studying genetics from scratch, it links to a second lens which has some tutorial videos to help explain the fundamentals.)The two lenses are broadly similar so choose either male XX or female XY according to your interest.
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Female XX Karyotype
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Karyotype is the technical term for the number of chromosomes: humans usually have 23 pairs, making 46 chromosomes in all. Some animals have more; some less. For sex determination, the 23rd pair is the most important and strongly influences whether...
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Male 46,XY Karyotype
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The <a href="http://www.squidoo.com/human-karyotype" target="_blank">standard human karyotype</a> is made up of 23 pairs of chromosomes, giving 46 chromosomes in total. Human sex is determined by the final pair which...
Androgen Insensitivity Syndrome
It might be thought that those who have a 46,XY karyotype are men and those with a 46,XX karyotype are women. It's not that straightforward.
Certain women have an insensitivity to androgens - to male hormones. That is, male hormones don't have their usual effect. Women who have a genetic condition known as Androgen Insensitivity Syndrome, AIS. These women have 46,XY karyotype but develop as women with normal female primary and secondary sexual characteristics (although they may not develop ovaries).
Androgen insensitivity syndrome (AIS), also referred to as androgen resistance syndrome, is a set of disorders of sex development caused by mutations of the gene encoding the androgen receptor. The set of resulting disorders varies according to the structure and sensitivity of the abnormal receptor. Most forms of AIS involve a variable degree of undervirilization and/or infertility in XY persons of either gender. A person with complete androgen insensitivity syndrome (CAIS) has a female external appearance despite a 46XY karyotype and undescended testes, a condition once called "testicular feminization" a phrase now considered both derogatory and inaccurate.
Since 1990, major scientific advances have greatly expanded medical understanding and management of the molecular mechanisms of the clinical features of AIS. Importantly, advocacy groups for this and other intersex conditions have increased public awareness and spurred acceptance and understanding of the variable nature of gender identity. The value of accurate and scientifically detailed information for patients is now emphasized, with physicians no longer automatically recommending traditional surgical corrections, with elective option now viewed as a possible but no longer necessary intervention for ambiguous conditions.
Other Genetic Intersex Conditions
The situation is even more complicated then AIS would suggest. Some individuals may have a karyoype other than 46,XX or 46,XY. They for instance have an extra chromosome, such as 47,XXY. Other intersex conditions are even more complex and may for instance involve a mix of different karyotpes. This is referred to as mosaicism.-
Klinefelter's Disease
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Klinefelter's Disease is a genetic conditon affecting about 1 in 750 men in which they have an additional chromosome in pair 23. There may be no symptoms other than a difficulty fathering children.
No Reliable Gender Test
About Kate Phizackerley
(Introducing your lensmistress)
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Guestbook
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Icons I Love
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I user icons from a number of designers on many of my lenses. I've had a short dedication at the bottom of most lenses but decided it was about time I created a lens where I can talk more about my choices and over time extend the repertoire. There is...
by Kate-Phizackerley
Off Squidoo I am a middle-aged woman with a wide range of interests from Ancient Egypt, backgammon, cookery ... to ... Zimbabwe which I visited 20 y... (more)
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