Anabolic Steroids – Cycles, Doses, Side Effects
Anabolic steroids are often associated with the world of bodybuilding and sports, where their use is controversial and sometimes illegal. However, they are used by a variety of people for different purposes, from improving athletic performance to enhancing physical appearance.
In this article, we will explore the fascinating world of anabolic steroids, including what they are, how they work, and the benefits and risks associated with their use.
Anabolic steroids have been used by athletes, bodybuilders, and fitness enthusiasts for decades. However, their use has extended beyond these communities, with some people using them for weight loss and other purposes.
According to a study published in the British Journal of Sports Medicine, approximately 3% of the global population has used anabolic-androgenic steroids (AAS) at some point in their lives. The history of anabolic steroids is also fascinating, from their initial development in the 1930s to their use by athletes in the 1950s and beyond.
The purpose of this article is to provide a comprehensive overview of anabolic steroids, including their chemical composition, benefits, side effects, risks, and legal status. We will explore the science behind anabolic steroids, how they affect the body, and what users can expect when using them.
This article is intended for anyone interested in using anabolic steroids for athletic performance or physical enhancement, as well as those who want to learn more about the effects of anabolic steroids on the body.
- 1 What Are Anabolic Steroids?
- 2 Benefits of Using Anabolic Steroids
- 3 Side Effects of Using Anabolic Steroids
- 4 Anabolic Steroids Dosage and Cycle
- 5 Risks and Dangers of Using Steroids
- 6 Anabolic Steroids and PEDs in Sports
- 7 Anabolic Steroids and the Law
- 8 Frequently Asked Questions
- 8.0.1 What synthetic steroids are best for muscle growth?
- 8.0.2 What synthetic steroids are best for muscle strength?
- 8.0.3 What steroids are best for increased energy levels?
- 8.0.4 What works best for increased hormonal levels?
- 8.0.5 Are They Illegal?
- 8.0.6 What do they do?
- 8.0.7 What are the best for women?
- 8.0.8 Can you tell me where to get some?
- 8.0.9 What are the best for bulking?
- 8.0.10 What are the best for cutting?
- 8.0.11 What is the best for strength?
- 8.1 Conclusion
What Are Anabolic Steroids?
Anabolic Steroids are synthetic hormones that mimic the effects of testosterone in the body. They are typically used to promote muscle growth, enhance athletic performance, and improve physical appearance. Anabolic steroids are derived from the hormone testosterone and are made up of carbon, hydrogen, and oxygen.
There are several different types of anabolic steroids, each with its unique properties and effects on the body. Some of the most common types of anabolic steroids include:
Testosterone: This is the primary male sex hormone and is responsible for the development of male sexual characteristics. Testosterone is also important for building muscle mass and increasing strength.
Dianabol: This is a highly potent steroid that is used to promote muscle growth and increase strength. It is also used to enhance athletic performance and improve physical appearance.
Deca-Durabolin: This steroid is used to promote muscle growth and increase strength. It is also used to treat conditions such as osteoporosis and anemia.
Winstrol: This steroid is used to promote muscle growth and increase strength. It is also used to enhance athletic performance and improve physical appearance.
Each type of steroid has its unique effects on the body, and the specific benefits and drawbacks will depend on the individual using the substance.
Anabolic steroids are sometimes used for medical purposes to treat conditions such as delayed puberty, muscle wasting, and osteoporosis. They can also be used to treat conditions such as breast cancer and anemia.
The use of anabolic steroids can have a number of potential side effects, some of which can be serious or even life-threatening. Some of the most common side effects of anabolic steroid use include:
- Hair loss
- Increased risk of heart disease
- Liver damage
- Mood swings
- Increased risk of infections
- Development of breast tissue in men (gynecomastia)
Long-term use of anabolic steroids can have several serious health consequences, including an increased risk of heart disease, liver damage, and other serious conditions.
Studies have also shown that anabolic steroid use can have a significant impact on mood and behavior, and can lead to increased aggression, irritability, and other psychological problems.
The use of anabolic steroids is illegal in most countries without a prescription. Additionally, their use is prohibited by most professional sports organizations and competitions.
The use of anabolic steroids can also be considered unethical, particularly in cases where they are used to gain an unfair advantage in competition.
Further research on anabolic steroids is essential to better understand their effects on the body and to develop safer and more effective treatments for medical conditions that may benefit from these drugs.
Additionally, it is important to continue to educate the public about the potential risks and dangers associated with anabolic steroid use.
How Do Anabolic Steroids Work?
Anabolic steroids are synthetic hormones that mimic the effects of testosterone in the body. They work by increasing protein synthesis within cells, which leads to an increase in muscle size and tissue growth.
Anabolic steroids also stimulate the production of red blood cells, which increases oxygen delivery to the muscles, allowing for greater endurance and performance during exercise.
Mechanism of Action
Anabolic steroids work by binding to androgen receptors in the body. These receptors are found on the surface of cells in various tissues throughout the body, including skeletal muscle, bone, and liver.
Once anabolic steroids bind to these receptors, they activate a series of signaling pathways that ultimately lead to an increase in protein synthesis and muscle growth.
Effects on Muscle Growth and Fat Loss
One of the primary ways that anabolic steroids affect the body is by increasing muscle growth and decreasing fat mass.
Anabolic steroids promote muscle hypertrophy by increasing protein synthesis and inhibiting protein breakdown. They also stimulate the production of insulin-like growth factor 1 (IGF-1), which is an important factor in muscle growth.
In addition to promoting muscle growth, anabolic steroids can also help to reduce body fat. This is because they increase metabolic rate, which leads to a greater rate of fat burning. Anabolic steroids also inhibit the storage of fat in adipose tissue by suppressing the activity of the enzyme lipoprotein lipase.
Effects on Hormone Levels and Metabolism
Anabolic steroids affect hormone levels and metabolism in many ways. They increase the production of testosterone in the body, which is important for muscle growth and recovery. They also decrease the production of cortisol, which is a catabolic hormone that can lead to muscle breakdown.
Anabolic steroids can also affect lipid metabolism, leading to increases in both HDL (good) and LDL (bad) cholesterol. This can increase the risk of cardiovascular disease if not managed properly. Anabolic steroids can also lead to insulin resistance, which can increase the risk of developing type 2 diabetes.
Importance of Medical Supervision
It is important to use anabolic steroids under medical supervision to minimize the risk of adverse side effects.
Anabolic steroid abuse can lead to a number of physical effects, including changes in mood and behavior. Prolonged use of anabolic steroids can also lead to serious health problems such as liver and kidney damage, and increased risk of cardiovascular disease.
Medical supervision is important to monitor the use of anabolic steroids and their effects on the body. A healthcare provider can help determine the appropriate dosage and duration of use, as well as monitor any potential adverse side effects. Blood tests may also be used to monitor hormone levels and liver function.
Additional Detail and Research
While anabolic steroids have been shown to have positive effects on muscle growth and fat loss, they can also have several adverse side effects.
These include weight gain, acne, hair loss, and increased risk of liver and kidney damage. Anabolic steroid abuse can also lead to several physical effects, including changes in mood and behavior.
Androgenic-anabolic steroids are classified as Schedule III controlled substances in the United States, which means that they can only be obtained with a prescription.
Anyone considering the use of anabolic steroids should consult with a healthcare provider to weigh the potential benefits and risks.
Benefits of Using Anabolic Steroids
Anabolic steroids are commonly used by athletes and bodybuilders to enhance their physical performance and improve their body composition. While there are risks associated with using anabolic steroids, there are also several benefits.
Benefits for Bodybuilding and Athletic Performance
One of the primary benefits of using anabolic steroids is their ability to increase muscle mass and strength.
By increasing protein synthesis and nitrogen retention in the muscles, anabolic steroids promote the growth of skeletal muscle, allowing athletes to train harder and recover faster. This is especially useful for bodybuilders, who require a high level of muscle mass and definition to compete at a professional level.
In addition to muscle growth, anabolic steroids also enhance endurance, allowing athletes to perform longer and more intensely during workouts and competitions. This is particularly beneficial for endurance athletes, such as runners and cyclists, who need to maintain a high level of stamina to succeed.
Enhancement of Strength and Endurance
Anabolic steroids increase the production of red blood cells in the body, leading to increased oxygenation of the muscles. This results in improved endurance and overall physical performance. Anabolic steroids also increase the synthesis of muscle proteins, which leads to increased strength and power.
Promotion of Lean Muscle Mass and Decrease in Body Fat
Anabolic steroids promote the growth of lean muscle mass, which is essential for athletes and bodybuilders.
By increasing muscle mass, anabolic steroids also increase the basal metabolic rate, allowing athletes to burn more calories and reduce body fat. This can lead to a more defined and aesthetically pleasing physique.
Research has also shown that anabolic steroids can help preserve muscle mass during periods of calorie restriction, such as during a cutting phase. This is important for bodybuilders who want to maintain their muscle mass while losing body fat.
Additional Research on the Benefits of Using Anabolic Steroids
There is a significant amount of research on the benefits of using anabolic steroids. Studies have shown that anabolic steroids can improve muscle strength and power, as well as increase muscle size and lean body mass.
Anabolic steroids can also have a positive impact on bone density, which is important for overall health and athletic performance. Additionally, anabolic steroids have been shown to improve collagen synthesis, which can lead to improved joint health and reduced risk of injury.
However, it is important to note that the use of anabolic steroids can also lead to several adverse effects, including liver damage, high blood pressure, and an increased risk of heart disease.
Other potential side effects of anabolic steroid use include acne, hair loss, and mood changes. It is important to weigh the risks and benefits before considering the use of anabolic steroids.
Side Effects of Using Anabolic Steroids
Steroids are synthetic hormones designed to mimic the androgenic effects of testosterone in the body.
While they can provide some benefits to athletes and bodybuilders, they also come with a range of side effects that can be harmful to health. In this section, we will discuss the potential side effects of using anabolic steroids in detail.
Potential Side Effects
The side effects of anabolic steroids can be both physical and psychological. Physical side effects can include liver damage, cholesterol issues, cardiovascular problems, and hormonal imbalances. Psychological side effects can include mood swings and aggression.
Risk of Liver Damage and Cholesterol Issues
Anabolic steroids can be toxic to the liver, and prolonged use can cause liver damage. Additionally, anabolic steroids can cause an increase in LDL cholesterol levels, which can increase the risk of heart disease.
Risk of Cardiovascular Problems
Anabolic steroids can increase the risk of cardiovascular problems such as high blood pressure, heart disease, and stroke. This is due to the fact that anabolic steroids can increase the level of LDL cholesterol in the body, which can lead to the formation of plaque in the arteries.
Psychological Side Effects
Anabolic steroids can cause a range of psychological side effects, including mood swings, irritability, and aggression. These side effects can be particularly dangerous for those who are already predisposed to mental health conditions such as depression or anxiety.
Risk of Hormone Imbalances and Fertility Issues
Anabolic steroids can disrupt the normal hormonal balance in the body, leading to a range of side effects such as acne, hair loss, and breast tissue development in men. Anabolic steroid use can also cause fertility issues in both men and women.
The long-term use of anabolic steroids can have serious health consequences, including an increased risk of cardiovascular disease, liver disease, and blood clots. Additionally, long-term use can cause irreversible changes such as facial hair growth and the development of masculine characteristics in women.
Understanding the Side Effects
There is a significant amount of research that has been conducted on the side effects of anabolic steroids.
Some studies have found that anabolic steroid use can cause testicular atrophy and stunted growth in young people, while others have found that it can increase the risk of developing body dysmorphic disorder.
It is important to note that the use of anabolic steroids is a class of drugs that are unapproved and may contain illegal substances. Therefore, it is crucial to seek medical advice before using anabolic steroids.
Anabolic Steroids Dosage and Cycle
Anabolic steroid dosage varies depending on the type of steroid, the individual’s experience level, and their desired results.
The following dosages are provided as general guidelines and should not be followed without consultation with a healthcare professional:
- Testosterone Cypionate: 200-500mg per week
- Dianabol: 15-50mg per day
- Deca-Durabolin: 200-400mg per week
- Winstrol: 25-100mg per day
- Anadrol: 25-150mg per day
- Trenbolone: 50-100mg every other day
How to Properly Cycle Anabolic Steroids
Cycling refers to the process of using steroids for a period of time, followed by a break to allow the body to recover.
The length of a steroid cycle and the frequency of administration varies depending on the individual’s experience level and desired results. A typical cycle length ranges from 6 to 12 weeks, with a break of at least 4 weeks in between cycles.
How to Stack Steroids for Optimal Results
Stacking refers to the use of multiple steroids or other compounds simultaneously to achieve a desired result.
While stacking can increase the effectiveness of steroids, it can also increase the risk of side effects and should be approached with caution. Consultation with a healthcare professional is strongly recommended.
Examples of Steroid Stacks
- Testosterone and Deca-Durabolin Stack: This stack is commonly used for bulking and can include a dosage of 500mg of testosterone per week and 400mg of Deca-Durabolin per week for a 12-week cycle.
- Dianabol and Winstrol Stack: This stack is commonly used for cutting and can include a dosage of 30-50mg of Dianabol per day and 50mg of Winstrol every other day for a 6-8 week cycle.
- Trenbolone and Anadrol Stack: This stack is commonly used for strength and can include a dosage of 100mg of Trenbolone every other day and 50mg of Anadrol per day for a 6-8 week cycle.
It’s important to note that the specific dosage and cycle for a steroid stack should be tailored to the individual user’s experience level, health status, and desired results.
Understanding of Steroid Dosage and Cycling
Research on anabolic steroid dosage and cycling are ongoing, and new information is constantly emerging. It’s important to stay up-to-date on the latest research and consult with a healthcare professional before starting or altering a steroid cycle.
Some factors that can impact steroid dosage and cycling include:
- Health status
- Experience level
- Desired results
It’s important to consider all of these factors when determining the appropriate dosage and cycle for anabolic steroids.
Risks and Side Effects of Anabolic Steroids
While anabolic steroids can provide desired results for bodybuilders and athletes, they also come with potential risks and side effects. These can include:
- Liver damage and tumors
- Increased risk of cardiovascular disease
- High blood pressure
- Mood swings and aggressive behavior
- Acne and other skin problems
- Gynecomastia (breast tissue growth in men)
- Testicular atrophy (shrinkage of the testicles)
- Women may experience menstrual irregularities, infertility, and virilization (masculinization” or development of male characteristics)
It’s important to note that these risks and side effects can occur even when following recommended dosages and cycles. The risks can be increased with higher dosages, longer cycle lengths, and stacking multiple compounds.
Other factors that can impact the risk of side effects include:
- Age and gender
- Health status
- Lifestyle factors (such as diet and exercise)
- Use of other drugs or medications
To minimize the risks associated with anabolic steroid use, it’s important to follow recommended dosages and cycles and to always consult with a healthcare professional before starting or altering a steroid cycle.
Additionally, it’s important to prioritize overall health and well-being by maintaining a balanced diet, engaging in regular exercise, and getting adequate rest and recovery time.
Research and Sources
It’s important to note that research on anabolic steroids is ongoing, and new information is constantly emerging. As such, it’s important to stay up-to-date on the latest research and to consult with a healthcare professional before starting or altering a steroid cycle.
Risks and Dangers of Using Steroids
Anabolic steroids are powerful hormones that can have serious health consequences if used incorrectly. When taken at high doses, they can cause a range of health problems, including liver damage, kidney damage, and an increased risk of cancer.
Health Risks Associated with using Steroids
The health risks associated with anabolic steroid use are numerous and can be severe. High doses of anabolic steroids can cause liver damage, including liver cancer and other chronic liver diseases.
Kidney damage is also a risk, which can lead to kidney failure and other kidney-related health problems.
In addition, anabolic steroid use has been linked to an increased risk of cardiovascular disease, including high blood pressure, heart attacks, and strokes.
Risk of Addiction and Dependence
Anabolic steroid use can also be highly addictive, leading to a condition known as anabolic steroid dependence.
This condition can cause individuals to continue using anabolic steroids despite the negative consequences to their health and well-being. The risk of addiction and dependence is particularly high among individuals who use anabolic steroids to enhance athletic performance or bodybuilding.
Long-Term Health Problems
Long-term use of anabolic steroids can lead to a range of health problems that can be irreversible in some cases.
Liver and kidney damage can occur with prolonged use, which can lead to chronic health problems such as cirrhosis and kidney failure. Additionally, anabolic steroid use has been linked to an increased risk of certain types of cancer, including liver cancer, prostate cancer, and breast cancer.
Understanding the Risks and Dangers
Recent research has shown that the risks associated with anabolic steroid use may be more severe than previously thought.
A study published in the Journal of Clinical Endocrinology and Metabolism found that anabolic steroid use was associated with a significantly increased risk of premature death, particularly from cardiovascular disease.
Another study published in the Journal of Hepatology found that anabolic steroid use was associated with a significantly increased risk of liver cancer.
Anabolic Steroids and PEDs in Sports
The use of anabolic steroids and other performance-enhancing drugs in sports has been a controversial topic for many years.
These substances have been used to enhance athletes’ physical performance and endurance, but at a high cost to their health and reputation.
Many athletes have been caught using steroids, leading to suspensions, fines, and even bans from their sports.
Consequences of Using Steroids in Professional Sports
The consequences of using anabolic steroids in professional sports can be severe. Athletes who are caught using steroids are typically suspended, fined, or even banned from their sport.
In addition to the legal and ethical consequences, the use of anabolic steroids can have long-term health effects, including liver damage, heart disease, and infertility.
Ethics of Using Anabolic Steroids and Other PEDs in Sports
The use of anabolic steroids and other performance-enhancing drugs raises ethical concerns in the world of sports.
Many believe that the use of these substances gives an unfair advantage to athletes and undermines the integrity of the competition. The use of steroids and other performance-enhancing drugs can also lead to physical harm and create a culture of pressure and competition that can negatively impact athletes.
Research on Anabolic Steroids and PEDs in Sports
Further research is needed to fully understand the effects of anabolic steroids and other performance-enhancing drugs on athletes and the sports world.
Studies have shown that the use of these substances can have serious health consequences and lead to long-term damage. In addition to medical research, there is an ongoing debate about how to best regulate and enforce policies around steroid use in sports.
Anabolic Steroids and the Law
Anabolic steroids are classified as controlled substances in many countries, including the United States. This means that their use, sale, and possession without a prescription is illegal. The legal status of anabolic steroids varies from country to country, with some countries having stricter regulations than others.
In the United States, anabolic steroids are classified as Schedule III substances under the Controlled Substances Act. This means that they are considered to have a moderate to low potential for physical and psychological dependence. It is illegal to possess or sell anabolic steroids without a valid prescription from a licensed medical practitioner. The penalties for violating this law can include fines and imprisonment.
In Canada, anabolic steroids are also classified as controlled substances, but they are listed as Schedule IV substances. This means that they are considered to have a lower potential for abuse and dependence than Schedule III substances. However, it is still illegal to possess or sell anabolic steroids without a valid prescription from a licensed medical practitioner. The penalties for violating this law can include fines and imprisonment.
In the United Kingdom, anabolic steroids are classified as Class C drugs under the Misuse of Drugs Act. This means that they are considered to have a moderate potential for harm and abuse. It is illegal to possess or sell anabolic steroids without a valid prescription from a licensed medical practitioner. The penalties for violating this law can include fines and imprisonment.
Where Can You Legally Buy Steroids?
To purchase anabolic steroids legally and safely, it is important to have a valid prescription from a licensed medical practitioner.
Healthcare providers can prescribe anabolic steroids for legitimate medical conditions such as delayed puberty, muscle wasting, and osteoporosis. It is important to follow the prescribed dosage and duration of use to avoid potential health risks and legal consequences.
The consequences of purchasing anabolic steroids illegally can be severe. In addition to legal consequences, there are health risks associated with using counterfeit or unregulated products.
These products may contain harmful substances or incorrect dosages, which can lead to serious health complications such as liver damage, heart disease, and hormonal imbalances. It is important to only purchase anabolic steroids from a trusted source to avoid these risks.
Moreover, the regulations in place for the use and prescription of anabolic steroids vary from country to country. In some countries, anabolic steroids are only available with a prescription for legitimate medical purposes, while in others they are completely illegal.
In some countries, such as the United States, there are legal and medical guidelines for the use of anabolic steroids in sports, while in others there are no regulations in place. It is important to understand the regulations in your country before purchasing or using anabolic steroids.
In conclusion, the legal status of anabolic steroids varies from country to country, and it is important to follow the regulations in place to avoid legal consequences and health risks.
It is recommended to only purchase anabolic steroids with a valid prescription from a licensed medical practitioner and a trusted source to avoid the risks associated with counterfeit or unregulated products.
Healthcare providers can provide additional information on the safe and legal use of anabolic steroids.
Frequently Asked Questions
What synthetic steroids are best for muscle growth?
For larger muscles check out Dianabol, and Deca Durabolin.
What synthetic steroids are best for muscle strength?
For better muscle strength, check out Anadrol and Testosterone.
What steroids are best for increased energy levels?
For increased energy levels, check out Andriol and Anavar.
What works best for increased hormonal levels?
For greater hormonal levels, check out Human Growth Hormone.
Are They Illegal?
In the United States and most other countries around the world, you can obtain anabolic steroids legally in a couple of different ways. First, you can purchase topical (corticosteroids) over the counter.
These cortisone creams provide relief from itching and swelling at the surface of the skin, but because their mechanisms are different, they do not provide any performance enhancement benefits. Second, certain anabolics are legal with a prescription.
Millions of men around the world use them regularly to treat low testosterone, and physicians may prescribe them to treat autoimmune disorders or to increase bone density.
Although it is legal to possess, use, and buy in certain countries, most governments consider them controlled substances. This means that possession, use, and purchase may have legal consequences.
Be certain that you understand the laws in your area before you decide to buy.
What do they do?
What are the best for women?
There are only a few anabolics for women. Remember that these compounds are derivatives of testosterone, and too much testosterone in the female body causes serious issues. As such, the best choices for women include:
- Primobolan Depot
- Anadrol (the most popular by far)
Can you tell me where to get some?
There are several places where you can find for sale. You can purchase them from your pharmacy with a prescription from your physician, but if you want to use for performance enhancement reasons, this may prove difficult.
You could purchase them over the counter in another country, but this also poses problems in terms of travel and import laws. Fortunately, there are many ways to buy online.
You should avoid purchasing from “street” dealers, and you should even steer clear of guys in your gym that may offer them to you. You have no way to know what is in these products, and you may be throwing your money away or putting your health at risk.
What are the best for bulking?
What are the best for cutting?
They best help you burn body fat at the subcutaneous and visceral levels, but they do not influence your muscle growth. Some of the most popular include Winstrol, Primobolan, and Anavar.
What is the best for strength?
If you are interested in athletic performance enhancement, whether you want to bulk up, harden muscle, or cut body fat levels, you can find anabolics for sale online that provide outstanding results with minimal risk. Despite the social stigma surrounding anabolics, the truth is that they are safe with responsible use.
In this article, we have explored the various aspects of anabolic steroids, including their origins, mechanisms of action, and potential benefits.
We have also delved into the numerous risks and side effects associated with their use, emphasizing the importance of understanding these dangers before considering anabolic steroids as a means to enhance athletic performance or physical appearance.
It is crucial to remember that the use of anabolic steroids carries significant risks and dangers. These can range from short-term side effects, such as acne and mood swings, to long-term health consequences, including liver damage, cardiovascular issues, and hormonal imbalances.
Additionally, using anabolic steroids without proper medical supervision may result in severe legal penalties and damage to one’s reputation.
As a final note, we strongly encourage anyone considering the use of anabolic steroids to seek professional advice from a qualified healthcare provider.
It is essential to weigh the potential risks against any perceived benefits and make an informed decision based on accurate information and expert guidance.
- National Institute on Drug Abuse (NIDA): “Anabolic Steroids DrugFacts”: https://www.drugabuse.gov/publications/drugfacts/anabolic-steroids
- Mayo Clinic: “Performance-enhancing drugs: Know the risks”: https://www.mayoclinic.org/healthy-lifestyle/fitness/in-depth/performance-enhancing-drugs/art-20046134
- World Anti-Doping Agency (WADA): “Prohibited List”: https://www.wada-ama.org/en/resources/science-medicine/prohibited-list-documents
- The Journal of Clinical Endocrinology & Metabolism: “Adverse Health Consequences of Performance-Enhancing Drugs: An Endocrine Society Scientific Statement”: https://academic.oup.com/jcem/article/99/6/2005/2537391
- National Center for Biotechnology Information (NCBI): “Anabolic Steroids and the Athlete”: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2439524/
- National Library of Medicine (NLM): “Anabolic steroid abuse and dependence”: https://pubmed.ncbi.nlm.nih.gov/11054601/
- National Center for Biotechnology Information (NCBI): “Anabolic Steroids: A Review for the Clinician”: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2439527/