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]

Sssspectacular: Tree Snakes in Australia Can Actually Jump

sirichai_raksue/iStock via Getty Images
sirichai_raksue/iStock via Getty Images

Ophidiophobia, or fear of snakes, is common among humans. We avoid snakes in the wild, have nightmares about snakes at night, and recoil at snakes on television. We might even be born with the aversion. When researchers showed babies photos of snakes and spiders, their tiny pupils dilated, indicating an arousal response to these ancestral threats.

If you really want to scare a baby, show them footage of an Australian tree snake. Thanks to researchers at Virginia Tech, we now know these non-venomous snakes of the genus Dendrelaphis can become airborne, propelling themselves around treetops like sentient Silly String.

That’s Dendrelaphis pictus, which was caught zipping through the air in 2010. After looking at footage previously filmed by her advisor Jake Socha, Virginia Tech Ph.D. candidate Michelle Graham headed for Australia and built a kind of American Ninja Warrior course for snakes out of PVC piping and tree branches. Graham observed that the snakes tend to spot their landing target, then spring upward. The momentum gets them across gaps that would otherwise not be practical to cross.

Graham next plans to investigate why snakes feel compelled to jump. They might feel a need to escape, or continue moving, or do it because they can. Two scientific papers due in 2020 could provide answers.

Dendrelaphis isn’t the only kind of snake with propulsive capabilities. The Chrysopelea genus includes five species found in Southeast Asia and China, among other places, that can glide through the air.

[h/t National Geographic]

9 Facts About Narcolepsy

Korrawin/iStock via Getty Images
Korrawin/iStock via Getty Images

Everyone experiences occasional daytime sleepiness, but just a small fraction of the population knows what it’s like to have narcolepsy. The disorder is defined by persistent drowsiness throughout the day, and in some cases, sleep paralysis, hallucinations, and the sudden loss of muscle control known as cataplexy. Having narcolepsy can make doing everyday activities difficult or dangerous for patients, but unlike some chronic conditions, it’s also easy to diagnose and treat. Here are some facts you should know about the condition.

1. There are two types of narcolepsy.

If everything you know about narcolepsy comes from movies and TV, you may think of it as the disease that causes people to go limp without warning. Sudden loss of muscle control is called cataplexy, and it’s the defining symptom of type 1 narcolepsy. Type 2 narcolepsy, on the other hand, is mainly characterized by fatigue. Losing motor function while awake isn’t a problem for those with type 2.

2. Type 1 narcolepsy stems from a chemical deficiency.

Almost every patient with type 1 narcolepsy has low levels of hypocretin. Hypocretin is a neurochemical that regulates the wake-sleep cycle. When there isn’t enough of this chemical in the brain, people have trouble staying conscious and alert throughout the day. Most people with the second, less severe type of narcolepsy have normal hypocretin levels, with about a third of them producing low or undetectable amounts. Type 2 narcoplepsy has been studied far less than type 1 of the disorder, and scientists are still figuring out what causes it.

3. The exact causes of narcolepsy aren’t always clear.

So why do some people’s brains produce less hypocretin than others? That part has been hard for scientists to figure out. One possible explanation is that certain autoimmune disorders cause the body to attack the healthy brain cells that make this chemical. This disorder can be the result of genetic and environmental factors. Although people with narcolepsy rarely pass it down to their offspring (this happens less than 1 percent of the time), the sleep condition does occasionally crop up in family clusters, suggesting there is sometimes a genetic component at play. Head trauma that impacts the area of the brain responsible for governing sleep can also lead to narcolepsy in rare cases.

4. There are tests to diagnose narcolepsy.

If patients believe they might have narcolepsy, their doctors might ask them to detail their sleep history and keep a record of their sleep habits. There are also a few tests potential narcoleptics can take to determine if they have the condition. During a polysomnography test, patients spend the night at a medical facility with electrodes attached to their heads to monitor their breathing, eye movement, and brain activity. A multiple sleep latency test is similar, except it gauges how long it takes patients to fall asleep during the day.

5. Strong emotions can trigger cataplexy.

Cataplectic spells can sometimes be predicted by triggers. In some patients, feeling strong emotions—whether they’re crying, laughing, angry, or stressed—is all it takes for them to lose muscle control. These triggers vary from patient to patient, and they can even affect the same person randomly. Some people deal with them by avoiding certain situations and closing themselves off emotionally, which can disrupt their social lives.

6. Narcolepsy can make sleep terrifying.

Narcoleptics don’t just worry about their disorder during their waking hours. When they’re trying to fall asleep at night or wake up in the morning, narcolepsy can complicate things. One symptom is experiencing vivid, dream-like hallucinations while transitioning in or out of consciousness. These visions are often scary and may involve an intruder in the room with the sleeper. If they happen as the patient falls asleep, the hallucinations are called hypnagogic, and if they occur as they wake up, they’re hypnopompic.

A related symptom is sleep paralysis. This happens when a person’s brain cuts off muscle control of their body before they’re fully asleep or as they’re waking up. This combined with hypnagogic or hypnopompic nightmares can cause frightening experiences that are sometimes confused for real encounters.

7. Narcoleptics sometimes do activities half-asleep.

To outside observers, narcolepsy is sometimes hard to spot. A narcoleptic patient overcome by sleepiness won’t necessarily pass out in the middle of what they’re doing. Some act out “automatic behavior,” which means they continue with their actions—whether that’s walking, driving, or typing—with limited consciousness. This can cause poor performance at work or school, and in worst case scenarios, accidents while driving a car or operating machinery.

8. Harriet Tubman may have had narcolepsy.

One of the most famous likely narcoleptics in history is Harriet Tubman. The African American abolitionist was known to suffer from what were probably sudden narcoleptic episodes. The condition may have stemmed from the severe head trauma she sustained when a slave master threw an iron at another slave and hit her instead. The injury left her with permanent brain damage: In addition to narcolepsy, she also experienced chronic seizures and migraines throughout her life.

9. Medications and lifestyle changes are common narcolepsy treatments.

Though there’s no way to cure narcolepsy completely, there are many treatment options available. Taking medication is one of the most common ways to manage the disorder. Stimulants such as modafinil and armodafinil can be used to combat mild sleepiness, while amphetamines are often prescribed for more severe forms of fatigue. For hallucinations and sleep paralysis, selective serotonin reuptake inhibitors and serotonin and norepinephrine reuptake inhibitors—drugs that suppress REM sleep—can help.

As an alternative or supplementary treatment to medications, doctors may recommend lifestyle changes. Sticking to a sleep schedule, exercising regularly, avoiding nicotine and alcohol, and taking naps during the day can all reduce the symptoms of narcolepsy.

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