True hermaphroditism is more common in South Africa than anywhere else in the world.
And specialists who deal with intersexed people in Gauteng say they're seeing a new patient every four to six weeks - less than 10 percent of the condition's estimated incidence in the province.
This revelation follows in the wake of the continuing furore around 800m world champion Caster Semenya.
It emerged this week that the 18-year-old Polokwane athlete had been gender- tested by the International Association of Athletics Federations before she went to Berlin for the World Championships last month, where she won a gold medal.
And the test was ordered by Athletics South Africa.
ASA boss Leonard Chuene has denied any knowledge of a South African test or ever consenting to such a test. Yesterday, however, newspapers published extracts of e-mails between ASA officials that fingered him.
It also emerged this week that Semenya's genitals were photographed during the humiliating sex tests.
The test results have not yet been officially released.
The ASA has petitioned President Jacob Zuma to appoint a commission of inquiry into the debacle.
This week Dr David Segal, a paediatric endocrinologist at Charlotte Maxeke Johannesburg Academic Hospital, said there was a greater incidence of true hermaphroditism, medically referred to as ovatesticular disorder of sex development, here than anywhere else in the world.
Segal, who also works at Wits University's Donald Gordon Medi-Clinic, explained this hermaphroditism meant a person was born with both testicular and ovarian tissue.
This results in there not being enough testosterone to form a normal boy and too much for a girl.
But what many people do not realise, Segal said, is that other conditions can lead to intersexuality.
These include androgen insensitivity syndrome, in which male development is prevented in chromosomal males because the body is not sensitive to androgen; cryptorchidism, in which one or both testes fail to move into the scrotum as the male foetus develops; and congenital adrenal hyperspadia, where the adrenal gland produces too much male hormones in a person, which triggers masculinity, especially in females.
According to the Intersex Society of North America, about one in 500 people are intersexed.
But Segal says there could be as many as one in 200 cases in South Africa.
In the past six years Segal has seen more than 100 cases of intersexuality. At the most, he receives one case a month.
"I work on a referral basis. A lot of it is not detected. I see a tenth of the cases.
"Some are sent to surgeons and you don't pick up the milder cases."
Then there are also cases that are misdiagnosed, he said.
"There are a whole bunch of cases with boys where they are referred to surgeons and neurologists instead of to endocrinologists. This is not the most appropriate decision as the endocrinologist should do the initial diagnosis, planning and counselling."
Another endocrinologist, Professor Barry Joffe, said many intersexed people went undiagnosed, especially in rural areas.
"In sophisticated societies, intersexed people may be recognised earlier (in life), but in a rural area it could be missed for a long time."
Also, some syndromes present themselves only later in childhood. This would be detected, for example, when girls failed to develop breasts or to menstruate.
Joffe said that at the most, he saw a case every month to two months in his practice. "It's rare but it's not totally uncommon."
Segal said intersexuality is still very stigmatised.
"There is also a massive misunderstanding of all the conditions. And the patients are embarrassed.
"A lot of parents are ashamed and blame themselves. They feel guilty about maybe smoking or drinking or doing drugs during a pregnancy. They wonder if things would have been different if they did anything differently.
"But it is almost never the fault of the parents. There is nothing you can do to prevent or fix it," said Segal.