What Makes These Dominican Children Grow Penises at Puberty?

BBC via Youtube
BBC via Youtube

In the Dominican Republic, the phenomenon of children who were raised female appearing to swap sexes at puberty is so common it even has a name. Guevedoces roughly translates to "penis [or "balls"] at 12," and it’s the result of a rare enzyme deficiency that delays crucial steps of male sexual development until puberty.

When guevedoces are born, they appear to have external female genitalia even though their genes and internal reproductive organs are male. Parents assume their children are girls and raise them as such. But when these children begin producing large amounts of testosterone at puberty, their testes descend and they grow a penis—in addition to all the other changes that come along with male adolescence. 

Sexual development normally begins in the womb, and the same is true for guevedoces. Whether the fetus has one X chromosome or two, for the first several weeks of development its genes follow the same blueprint for both sexes. Then, sometime around the eight-week mark, the sex chromosomes get to work. For males, the undeveloped gonads become testicles and they start to release male hormones, including testosterone. In a structure called the tubercle, an enzyme called 5-alpha-reductase converts the testosterone to a stronger hormone called dihydrotestosterone (DHT), which is necessary to develop external genitalia. It's this hormone that turns the tubercle into a penis; without it, it develops into a clitoris.

The rare enzyme deficiency found in guevedoces leaves them unable to develop external male genitalia in the womb. They still produce plenty of testosterone, which triggers the development of internal structures like the epididymis and vas deferens, but the lack of DHT makes the babies appear female at birth. It’s not until the second surge of testosterone these children receive at puberty that they grow testes and a penis. 

The condition is thought to be genetic, tracing back to the female founder of a small village in the Dominican Republic's mountainous hinterland. Outside of the nation, it’s incredibly rare.

For some guevedoces, being raised as female wasn’t an easy experience. “I never liked to dress as a girl, and when they bought me toys for girls, I never bothered playing with them,” Johnny, who had grown up as Felicita, told BBC Two, which features these kids in the second episode of the series Countdown to Life: The Extraordinary Making of You. “When I saw a group of boys, I would stop to play ball with them.” When Johnny, now 24, began to undergo physical changes, he was taunted at school and called nasty names by his classmates. He’s had a number of short-term girlfriends since going through puberty and dreams of one day getting married and starting a family. Another child named Carla began the process of transitioning to Carlos at age 9; he can be seen receiving a smile-inducing haircut in the photo above. 

Most people with this condition live out their adult lives as men, but some choose to undergo surgery and remain female. The discovery of this disorder in the 1970s led to the development of a best-selling drug called finasteride, which is commonly prescribed to treat benign enlargement of the prostate and male pattern baldness. (You may know it by the brand name Propecia.) The drug mimics the enzyme deficiency by blocking the action of 5-alpha-reductase.

You can learn more about this rare condition and the people who have it on the BBC Two series Countdown to Life: The Extraordinary Making of You

[h/t: BBC]

A Simple Skin Swab Could Soon Identify People at Risk for Parkinson's

iStock.com/stevanovicigor
iStock.com/stevanovicigor

More than 200 years have passed since physician James Parkinson first identified the degenerative neurological disorder that bears his name. Over five million people worldwide suffer from Parkinson’s disease, a neurological condition characterized by muscle tremors and other symptoms. Diagnosis is based on those symptoms rather than blood tests, brain imaging, or any other laboratory evidence.

Now, science may be close to a simple and non-invasive method for diagnosing the disease based on a waxy substance called sebum, which people secrete through their skin. And it’s thanks to a woman with the unique ability to sniff out differences in the sebum of those with Parkinson's—years before a diagnosis can be made.

The Guardian describes how researchers at the University of Manchester partnered with a nurse named Joy Milne, a "super smeller" who can detect a unique odor emanating from Parkinson's patients that is unnoticeable to most people. Working with Tilo Kunath, a neurobiologist at Edinburgh University, Milne and the researchers pinpointed the strongest odor coming from the patients' upper backs, where sebum-emitting pores are concentrated.

For a new study in the journal ACS Central Science, the researchers analyzed skin swabs from 64 Parkinson's and non-Parkinson's subjects and found that three substances—eicosane, hippuric acid, and octadecanal—were present in higher concentrations in the Parkinson’s patients. One substance, perillic aldehyde, was lower. Milne confirmed that these swabs bore the distinct, musky odor associated with Parkinson’s patients.

Researchers also found no difference between patients who took drugs to control symptoms and those who did not, meaning that drug metabolites had no influence on the odor or compounds.

The next step will be to swab a a much larger cohort of Parkinson’s patients and healthy volunteers to see if the results are consistent and reliable. If these compounds are able to accurately identify Parkinson’s, researchers are optimistic that it could lead to earlier diagnosis and more effective interventions.

[h/t The Guardian]

World’s Oldest Stored Sperm Has Produced Some Healthy Baby Sheep

A stock photo of a lamb
A stock photo of a lamb
iStock.com/ananaline

It’s not every day that you stumble across a 50-year-old batch of frozen sheep sperm. So when Australian researchers rediscovered a wriggly little time capsule that had been left behind by an earlier researcher, they did the obvious: they tried to create some lambs. As Smithsonian reports, they pulled it off, too.

The semen, which came from several prize rams, had been frozen in 1968 by Dr. Steve Salamon, a sheep researcher from the University of Sydney. After bringing the sample out of storage, researchers thawed it out and conducted a few lab tests. They determined that its viability and DNA integrity were still intact, so they decided to put it to the ultimate test: Would it get a sheep pregnant? The sperm was artificially inseminated into 56 Merino ewes, and lo and behold, 34 of them became pregnant and gave birth to healthy lambs.

Of course, this experiment wasn’t just for fun. They wanted to test whether decades-old sperm—frozen in liquid nitrogen at -320°F—would still be viable for breeding purposes. Remarkably, the older sperm had a slightly higher pregnancy rate (61 percent) than sheep sperm that had been frozen for 12 months and used to impregnate ewes in a different experiment (in that case, the success rate was 59 percent).

“We believe this is the oldest viable stored semen of any species in the world and definitely the oldest sperm used to produce offspring,” researcher Dr. Jessica Rickard said in a statement.

Researchers say this experiment also lets them assess the genetic progress of selective breeding over the last five decades. “In that time, we’ve been trying to make better, more productive sheep [for the wool industry],” associate professor Simon de Graaf said. “This gives us a resource to benchmark and compare.”

[h/t Smithsonian]

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