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Introduction

SARMs are a shortened term for selective androgen receptor modulators.

These are a class of androgen receptor ligands that bind to androgen receptors in the body and activate androgenic signaling pathways.

In essence, they are a modified form of testosterone used in hormone replacement therapy and steroids.

The initial idea behind the development of SARMs was to create a drug with anabolic effects on skeletal muscle and bone, whilst avoiding negative effects in other tissues.

Such a drug could hypothetically be useful at replacing testosterone use in clinical settings, which comes with many adverse side effects.

As they are touted as a steroid alternative without the side effects, it is not surprising how their popularity is rapidly growing.

At the moment SARMs are purely regarded as research chemicals, however it is well documented that physique competitors and athletes are experimenting with these products on the black market.

They have only recently started to be studied in animals and humans, so there safety is largely unknown. SARMs are not currently approved for use in humans.

The Role Of SARMs?

Testosterone is the key male sex hormone that regulates fertility, muscle mass, fat distribution, and red blood cell production.

Low testosterone levels can cause many issues such as fatigue, anemia, low sex drive, and a loss of muscle and bone mass.

SARMs were originally developed to combat some serious common issues that occur with the elderly patients when their testosterone levels start to naturally decline and they become susceptible to sarcopenia and osteoporosis.

Age-associated loss of muscle mass and strength increases the risk of falls, fractures, mobility limitation, physical disability, and lowers quality of life [1].

However, the use of supraphysiologic doses of testosterone is commonly associated with a long list of adverse effects [2]. Common side effects include:

  • Acne
  • Gynecomastia
  • Enlarged prostate
  • Testicular shrinkage
  • Liver damage
  • Increased blood pressure.

SARMs were developed to be tissue-specific and only attach to receptors in the muscle and bone to avoid the dose-limiting adverse effects on other tissues that happens with standard testosterone or steroid usage.

How Do SARMs Work?

SARMS work like hormones, which are chemical mediators in your body. They attach to certain receptors in the body and exert their effects depending on the intensity and duration of the binding.

This is defined as being “tissue-selective”, meaning they are only meant to receptors that are needed to produce the desired effect of the drug. They do not intend to interfere with the receptors of prostate, liver, kidneys or brain which makes them a potentially safer option to steroids.

Specifically, SARMs are created to attach to receptors in skeletal muscle and bone to activate pathways involved in skeletal muscle hypertrophy and bone regeneration.

At least in animal studies, SARMs have shown to partially achieve this, with compounds such as S1 and S4 binding to androgen receptors with high affinity and demonstrating tissue selectivity. However, they still do not appear to be only specific to the target receptors, and unintentional biding to external receptors is still apparent [3].

Another one of the main advantages of SARMS is that, unlike testosterone, most of them do not get converted into 5α-DHT [4]. In addition, they do not appear to undergo aromatization into estrogen which could reduce the occurrence of side effects such as gynecomastia.

The tissue selectivity component of SARMs seems to be related to their tissue-specific expression of coregulatory proteins [5].

The Different Types Of SARMs

There are many different types of SARMs that each have their own unique benefits.

Some well-known SARMs are:

  • GW-501516 (cardarine)
  • SR9009 (stenabolic)
  • MK-677 (Ibutamoren or Nutrobal)
  • LGD-4033 (anabolicum)
  • MK-2866 (Ostarine)
  • S4 (andarine)
  • RAD140 (Testolone)

The Benefits Of SARMs

While several other SARMs have been tested clinically for various diseases, they have not advanced beyond phase II proof-of-concept. This is the stage where pilot studies are done on a relatively smaller number of patients in order to judge the efficacy and safety of the investigational drug.

May Increase Lean Body Mass

It is clear from studies that analyse muscle biopsies that testosterone administration can induce muscular hypertrophy in both type I and type II muscle fibers [6].

The testosterone-induced muscular hypertrophy is mainly due to an increase in satellite cell and myonuclear number [7], as well as increasing the amount of protein synthesis and inhibiting protein degradation [8].

SARMs have similar effects to low doses of testosterone, but to a lesser extent.

The extent of lean body mass gain depends greatly on the specific SARM is question, however most SARMs in pre-clinical animal trials saw at least significant increases in lean body mass, and on many occasions led to reductions in fat mass [10].

In human trials the benefits of SARM use is still apparent but the results are more modest, with a typical 1-2kg gain in fat-free mass over 4-6 weeks. In contrast, supraphysiological doses of testosterone enanthate can add over 5kg in the same period of time.

However, what is promising is that even in cancer patients going through periods of severe muscle wasting, the introduction of SARMs has demonstrated significant increases in lean body mass and better overall physical functioning [9].

There is still a lot more human research that needs to be done on SARMs to fully analyze their benefits.

SARMs Safety And Side Effects

SARMs have not been deemed safe for human use, as there are very few human studies on SARMs due to the many health concerns associated with their use.

Most of the research on SARMs is in animal models and even then some fairly serious side effects have been noted – despite the intention for SARMs to avoid the negative aspects of testosterone use.

Some of these serious side effects noted in animal and human research are:

  • Suppression of natural testosterone
  • Baldness
  • Gynecomastia
  • Blurred vision

Importantly, as they are not available to purchase through legitimate pharmaceutical companies, users have to resort to getting them through the unregulated black market. Therefore, the quality and safety of these compounds cannot be known.

When SARMs from underground labs have been tested, ~60% contain ingredients that were not stated on the label.

In fact, the Food and Drug Administration recently issued warning letters to 3 SARM companies in the United States due to major concerns about the potentially dangerous ingredients and lack of safety procedures during manufacturing.

In an official statement they said the following:

“Life threatening reactions, including liver toxicity, have occurred in people taking products containing SARMs. SARMs also have the potential to increase the risk of heart attack and stroke, and the long-term effects on the body are unknown”

Conclusion

SARMS are a selective androgen receptor modulators, which are drugs that bind to androgen receptors in the body, activate androgenic signaling pathways, and thus upregulate muscle and bone metabolism.

These drugs are intended to be used as a future replacement for testosterone, which can have many different side effects and are dangerous at high doses.

The current studies on SARMs do show a benefit to improving body composition, however to a far lesser extent than standard testosterone therapy.

The safety of SARMs is largely unknown, and they are currently not advised for human use.

Shaun Ward MSc BSc SENr Anutr
Shaun Ward MSc BSc SENr Anutr
Staff Writer & Fact Checker at DietProbe
Shaun is a registered nutritionist, and sport and exercise nutritionist, with experience in coaching professional endurance and strength athletes.
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This article has been reviewed and fact-checked by a certified nutritionist, and only uses information from credible academic sources.