Tag: sex hormones

Categories : CancerTags :

Scientists Figure out Paradoxical Effect of Testosterone in Prostate Cancer

On By ModernMedia
Ball and stick 3D model of testosterone. Source: Wikimedia CC0

A treatment paradox has recently come to light in prostate cancer: Blocking testosterone production halts tumour growth in early disease, while elevating the hormone can delay disease progression in patients whose disease has advanced.

The inability to understand how different levels of the same hormone can drive different effects in prostate tumours has been an impediment to the development of new therapeutics that exploit this biology.

Now, a Duke Cancer Institute-led study appearing in Nature Communications, provides the needed answers to this puzzle.

The researchers found that prostate cancer cells are hardwired with a system that allows them to proliferate when the levels of testosterone are very low. But when hormone levels are elevated to resemble those present in the normal prostate, the cancer cells differentiate.

“For decades, the goal of endocrine therapy in prostate cancer has been to achieve absolute inhibition of androgen receptor function, the protein that senses testosterone levels,” said lead investigator Rachid Safi, PhD, research assistant professor in the Department of Pharmacology and Cancer Biology, at Duke University School of Medicine.

“It’s been a highly effective strategy, leading to substantial improvements in overall survival,” he said. “Unfortunately, most patients with advanced, metastatic disease who are treated with drugs to inhibit androgen signaling will progress to an aggressive form of the disease for which there are limited therapeutic options.”

Using a combination of genetic, biochemical, and chemical approaches, the research team defined the mechanisms that enable prostate cancer cells to recognise and respond differently to varying levels of testosterone, the most common androgenic hormone.

It turned out to be rather simple. When androgen levels are low, the androgen receptor is encouraged to “go solo” in the cell. In doing so, it activates the pathways that cause cancer cells to grow and spread. However, as androgens rise, the androgen receptors are forced to “hang out as a couple,” creating a form of the receptor that halts tumour growth.

“Nature has designed a system where low doses of hormones stimulate cancer cell proliferation and high doses cause differentiation and suppress growth, enabling the same hormone to perform diverse functions,” McDonnell said.

In recent years, clinicians have begun treating patients with late-stage, therapy resistant prostate cancers using a monthly, high-dose injection of testosterone in a technique called bi-polar androgen therapy, or BAT. The inability to understand how this intervention works has hindered its widespread adoption as a mainstream therapeutic approach for prostate cancer patients.

“Our study describes how BAT and like approaches work and could help physicians select patients who are most likely to respond to this intervention,” McDonnell said. “We have already developed new drugs that exploit this new mechanism and are bringing these to the clinic for evaluation as prostate cancer therapeutics.”

Source: Duke University

Categories : Diet and NutritionTags :

Time to Debunk Four Persistent Myths about Intermittent Fasting

On By ModernMedia
Photo by Malvestida on Unsplash

In a new article published in Nature Reviews Endocrinology, researchers at the University of Illinois Chicago debunk four common myths about the safety of intermittent fasting. 

Intermittent fasting as a weight loss method has grown increasingly popular, with a large body of research demonstrating its safety. Despite this, several myths about fasting have spread among clinicians, journalists and the general public: that fasting can lead to a poor diet or loss of lean muscle mass, cause eating disorders, or decrease sex hormones. 

In a new commentary, UIC researchers debunk each of these. They base their conclusions on clinical studies, some of which they conducted and some done by others. 

“I’ve been studying intermittent fasting for 20 years, and I’m constantly asked if the diets are safe,” said lead author Krista Varady, professor of kinesiology and nutrition at UIC. “There is a lot of misinformation out there. However, those ideas are not based on science; they’re just based on personal opinion.”  

There are two main types of intermittent fasting. With alternate-day eating, people alternate between days of eating a very small number of calories and days of eating what they want. With time-restricted eating, people eat what they want during a four- to 10-hour window each day, then don’t eat during the rest of the day. The researchers conclude both types are safe despite the popular myths.

Their conclusions: 

Intermittent fasting does not lead to a poor diet: The researchers point to studies showing the intake of sugar, saturated fat, cholesterol, fibre, sodium and caffeine do not change during fasting compared with before a fast. And the percentage of energy consumed in carbohydrates, protein and fat doesn’t change, either.  

Intermittent fasting does not cause eating disorders: None of the studies show that fasting caused participants to develop an eating disorder. However, all the studies screened out participants who had a history of eating disorders, and the researchers say that those with a history of eating disorders should not try intermittent fasting. They also urge paediatricians to be cautious when monitoring obese adolescents if they start fasting, because this group has a high risk of developing eating disorders. 

Intermittent fasting does not cause excessive loss of lean muscle mass: The studies show that people lose the same amount of lean muscle mass whether they’re losing weight by fasting or with a different diet. In both cases, resistance training and increased protein intake can counteract the loss of lean muscle. 

Intermittent fasting does not affect sex hormones: Despite concerns about fertility and libido, neither oestrogen, testosterone nor other related hormones are affected by fasting, the researchers said. 

Source: University of Illinois Chicago