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Study on Muscle Growth in Healthy Aging and Sarcopenia Patients Using Testosterone Undecanoate and Placebo

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on understanding how human muscles might remember past exposure to testosterone, a hormone important for muscle growth. The study is particularly interested in conditions like healthy aging and sarcopenia, which is the loss of muscle mass and strength as people age. The trial will also explore issues related to anabolic resistance, which is when muscles do not grow as expected in response to exercise or hormones, and anti-doping concerns in sports.

The study will use two treatments: Nebido, which contains testosterone undecanoate, and a placebo. Participants will be divided into groups, with some receiving the testosterone treatment and others receiving the placebo. The main goal is to see if muscles can grow back to their previous size and strength after stopping testosterone for a while. This will be compared between those who had testosterone before and those who did not.

Participants will undergo a series of tests to measure changes in muscle size, strength, and other characteristics. These tests will include methods like DEXA scans, which are used to measure body composition, and muscle biopsies, which involve taking a small sample of muscle tissue for analysis. The study will also look at how muscle cells change at a genetic level, including changes in DNA methylation, which is a process that can affect how genes are turned on or off. The trial aims to provide insights into how muscles respond to testosterone and how this might be used to improve muscle health in older adults.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, you will be asked to provide written informed consent. This confirms your understanding and agreement to participate in the trial.

  2. Step 2

    Initial assessments

    You will undergo initial assessments, which include a medical questionnaire, a physical examination, routine blood tests, and urine samples. These assessments ensure you meet the study's criteria: being a sedentary male aged 55-70, with morning serum testosterone levels greater than 8 nmol/L, and without any known illnesses or conditions.

  3. Step 3

    Treatment phase

    During the treatment phase, you may receive either a placebo or testosterone undecanoate through an intramuscular injection. The testosterone undecanoate is administered as a solution for injection at a dosage of 1000 mg/4 ml. The frequency and duration of administration will be specified by the study team.

  4. Step 4

    Monitoring and assessments

    Throughout the trial, your progress will be monitored through various assessments. These include measuring changes in fat-free mass, muscle size, and muscle fiber types using techniques like DEXA scans, ultrasound, and muscle biopsies. Additionally, strength, velocity, and power will be evaluated using equipment such as the Keiser leg press machine and isokinetic dynamometry.

  5. Step 5

    Conclusion of the trial

    The trial is expected to conclude by September 30, 2025. At the end of the study, final assessments will be conducted to compare the ability to retrain and enhance muscle size after a period of detraining or testosterone abstinence between the testosterone and placebo groups.

Who can join the trial?

6 criteria

  • Sedentary males - Men who do not engage in regular physical activity.
  • Aged 55-70 years old.
  • Have serum testosterone levels greater than 8 nmol/L, measured in the morning. Serum testosterone is the amount of testosterone in the blood.
  • Do not have any known illness, disease, or other medical conditions.
  • Have completed a screening process, which includes a medical questionnaire, physical examination, routine blood tests, and urine samples.
  • Have provided written informed consent, meaning they have agreed to participate in the study after being informed about it.

Who cannot join the trial?

2 criteria

  • Participants must be **male**. Females cannot participate in this study.
  • Participants should not be part of a **vulnerable population**. This means they should not be in a group that needs special protection or care.
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Investigated drugs

Testosterone is a hormone that plays a key role in developing and maintaining male physical characteristics. In this clinical trial, testosterone is being used to see if it can help muscles grow bigger and stronger after a period of not using it. The study aims to find out if muscles can "remember" the effects of testosterone and respond better when it is used again after a break.

What is already known about the treatment

Testosterone – Testosterone is typically administered as an injection, patch, gel, or tablet, depending on the specific needs and preferences of the patient. In the context of current medical research, testosterone is being studied for its potential effects on muscle memory and growth, particularly after periods of reduced activity or abstinence. It is primarily used to address conditions like sarcopenia, which is the loss of muscle mass due to aging, and anabolic resistance, where the body does not respond well to muscle-building stimuli. At the molecular level, testosterone works by binding to androgen receptors in muscle cells, which then activate genes that promote muscle growth and repair. It is classified as an androgen, a type of hormone that plays a role in male traits and reproductive activity.

Investigated diseases

  • Healthy aging

    Healthy aging refers to the natural process of growing older while maintaining physical and mental well-being. It involves the gradual decline in bodily functions, such as muscle mass and bone density, which can affect mobility and strength. Cognitive functions may also change, with some decline in memory and processing speed. However, healthy aging emphasizes the ability to adapt to these changes and maintain a good quality of life. It is characterized by the absence of significant chronic diseases and the ability to engage in daily activities independently. Social engagement and mental health are also important aspects of healthy aging.

  • Sarcopenia

    Sarcopenia is the progressive loss of muscle mass and strength that occurs with aging. It begins to develop around the age of 30 and accelerates after the age of 60. This condition can lead to decreased mobility, increased risk of falls, and reduced ability to perform daily activities. Muscle fibers shrink and are replaced by fat and fibrous tissue, contributing to weakness. Sarcopenia is influenced by factors such as physical inactivity, poor nutrition, and hormonal changes. It is a major component of frailty in older adults.

  • Anabolic resistance

    Anabolic resistance is the reduced ability of the body to build muscle in response to protein intake or exercise. It is commonly observed in older adults and can contribute to muscle loss and weakness. This condition is characterized by a diminished response of muscle protein synthesis to dietary protein and physical activity. Factors contributing to anabolic resistance include aging, inflammation, and hormonal changes. It can lead to difficulties in maintaining muscle mass and strength, impacting overall physical function. Anabolic resistance is a key factor in the development of sarcopenia.

Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IITrial ID2023-507815-37-00Estimated enrolment40 patientsSponsorNorges Idrettshoegskole

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