Modern Australian

You need more than just testes to make a penis

  • Written by Mark Green, Merck Serono Senior Lecturer in Reproductive Biology, University of Melbourne

In prenatal ultrasounds or at delivery, many new parents look between their baby’s legs: the presence of a penis is taken as a strong sign that it’s a boy.

For humans and other animals, development of a penis was thought to be driven by “male hormones” (androgens) produced entirely by the testes of the male fetus as it grows in the uterus.

However, a new paper released today indicates this might not be the case. Instead, some of the masculinising hormones that drive penis development may come from other sources in the developing fetus. These include the liver, the adrenals (small glands found on the kidneys) and placenta.

For the first time, this work comprehensively looks at the possible sites of hormone production outside the testes and their role in regulating masculinisation – the process of gaining typical male characteristics. This helps us see how we develop as embryos, and might feed into a bigger picture of why disorders of penis development are increasing.

Read more: Our relationship with dick pics: it's complicated

Testosterone is not enough

The penis develops from an embryonic structure called the genital tubercle or GT.

The GT is present in both males and females, and develops into either a clitoris or penis, depending on its exposure to hormones secreted by the developing gonads (ovaries or testes).

In females, the developing ovaries do not produce early hormones and the GT becomes feminised, forming a clitoris.

In males, the developing testes produce testosterone. This circulates in the developing fetus and causes masculinisation of target tissues and induces penis development from the GT.

Testosterone itself is a relatively weak hormone. It is converted in the penis to another hormone called dihydrotestosterone (DHT), which has a much more potent masculinising effect.

It is the local conversion of testosterone to DHT within the tissue that is important for penis development and other changes.

There are several ways in which the fetus can make DHT. The most simple is via conversion from testicular testosterone (the so-called “canonical” pathway). However, DHT can also be produced via other steroid hormone pathways active in many tissues, which is explored further in this new paper.

Read more: What makes you a man or a woman? Geneticist Jenny Graves explains

Common birth defects

Understanding the pathways that control penis development is important. Disorders affecting penis development are among the most common birth defects seen in humans, with hypospadias (a disorder affecting development of the urethra) currently affecting around 1 in every 115 live males born in Australia, and rates are on the rise.

You need more than just testes to make a penis The urethra, the hole through which urine passes out of the body, is found in a range of different locations in the disorder known as hypospadias from www.shutterstock.com

In fact, the incidence of hypospadias has doubled over the past 40 years. Such a rapid increase in incidence has been attributed to environmental factors, with endocrine disrupting chemicals (EDCs) being proposed as a major cause. EDCs are man-made chemicals used in many industries – for example, in the production of plastics, cosmetics, flame retardants and pesticides. They can interfere with hormone and metabolic systems in our bodies.

Of the 1,484 EDCs currently identified, a large number are known to negatively affect male reproductive development.

Many studies have identified how EDCs negatively affect organs, such as the liver and adrenals, leading to diseases and disorders which damage the health of these organs and disturb male development.

Backdoor pathway

By measuring hormones from blood samples and tissues during the second trimester of human fetal development, this new research helps us understand the pathways driving the production of DHT, and masculinisation of the penis.

It suggests that in addition to the canonical pathway (testosterone from the testis converted to DHT in the GT and driving penis development), male steroids are synthesised by other organs, such as the placenta, liver and adrenal gland via a process called the “backdoor” pathway to contribute to masculinisation. Notably, the backdoor pathway was first discovered through research conducted here in Australia on marsupials.

The findings of this research suggest that EDCs might have effects in non-reproductive tissues, including the adrenals and liver, and then cause male reproductive diseases such as hypospadias.

Also, it indicates that placental defects, such as intrauterine growth restriction that results in babies being born small, might contribute to male reproductive diseases in humans.

Further research is now required to follow-up on these interesting findings to explore possible new causal pathways of disorders that begin during pregnancy.

Authors: Mark Green, Merck Serono Senior Lecturer in Reproductive Biology, University of Melbourne

Read more http://theconversation.com/you-need-more-than-just-testes-to-make-a-penis-111625

NEWS

could new opioid restrictions stop leftover medicines causing harm?

ShutterstockSeveral changes to the regulation of opioid supply in Australia come into effect today (June 1).Opioids are strong medicines used for pain. The new rules – including reducing pack sizes...

A time to embrace the edge spaces that make our neighbourhoods tick

ShutterstockAs we emerge from COVID-19 lockdowns, it is timely to reflect on how the design of our neighbourhoods and the ways we interact with them affect our lived experience.A clear...

6 easy ways to stop light pollution from harming our wildlife

ShutterstockAs winter approaches, marine turtle nesting in the far north of Australia will peak. When these baby turtles hatch at night, they crawl from the sand to the sea, using...

Australia's first service sector recession will be unlike those that have gone before it

ShutterstockAustralia is on the brink of its first recession in almost 30 years. The Australian Bureau of Statistics will deliver the official economic growth figure for the March quarter on...

3 ways plus a potted history

Alex Motoc/Unsplash, CC BYAs winter begins, porridge makes an excellent choice for breakfast. For many, porridge is redolent with memories of childhood. It is warm, filling, high in fibre and...

Lab experiments in the pandemic moved online or mailed home to uni students

hxdbzxy/ShutterstockThe COVID-19 pandemic has shaken university education, with most teaching moved off campus and students learning online at home.But a cornerstone of undergraduate science education has been a challenge: the...

Forget ‘murder hornets’, European wasps in Australia decapitate flies and bully dingoes

nutmeg66/flickr, CC BY-NCThe impacts of invasive mammals such as feral horses and feral cats have featured prominently in the media over the years.But the recent discovery of the infamous “murder...

As Minneapolis burns, Trump's presidency is sinking deeper into crisis. And yet, he may still be re-elected

Sipa USA Minneapolis Star Tribune/TNS/SipViolence has erupted across several US cities after the death of a black man, George Floyd, who was shown on video gasping for breath as a...

Digital-only local newspapers will struggle to serve the communities that need them most

ShutterstockThis week News Corp Australia announced the end of the print editions of 112 suburban and regional mastheads – about one-fifth of all of Australia’s local newspapers. Of those, 36...

Scott Morrison strengthens his policy power, enshrining national cabinet and giving it "laser-like" focus on jobs

Scott Morrison has won support for a major restructure of federal-state architecture which scraps the Council of Australian Governments, enshrines the “national cabinet” permanently, and pares down a plethora of...

Trump’s Twitter tantrum may wreck the internet

US President Donald Trump, who tweeted more than 11,000 times in the first two years of his presidency, is very upset with Twitter.Earlier this week Trump tweeted complaints about mail-in...

Government to repay 470,000 unlawful robodebts in what might be Australia's biggest-ever financial backdown

In a near-complete capitulation, the government will refund every alleged overpayment it has collected from welfare recipients under the discredited “robodebt” system of income averaging.Unveiling the automated system in mid-2016...

Popular articles from Modern Australian

Key Roles and Responsibilities of Criminal LawyersTop benefits of buying a house and land packageWhat is the role of a Weighted Blanket? How Can You Become a LifesaverWhat You Should Know About Front End Smash RepairsAdvantages of Living in a Retirement VillageIf you buy virtual currency, use a safe and secure exchangeUrban Development: Trends Shaping The Future of CitiesThree cities worth visiting in PolandUpgrade your career in beauty therapy with these short beauty courses6 Ways To Treat Obstructive Sleep Apnea (OSA)Top Tips for the Best Camping TripHealthy Cooking at Home - Tips & TricksMental Health and Covid-19: How Effective are Health- Supplements?Know the Best Times to Eat Protein Bars