The value of Vitamin D and Creatine in surpressing Myostatin.

I came across a link to this article on Muscular Development about Clenbuterol.Which is a Beta2-adrenergic agonist used to treat asthma.It's also used in bodybuilding to spare muscle,and burn fat.
See the MD article for more details.Benefits of Clenbuterol.
You can learn more about the use of Clenbuterol in bodybuilding from this article on Anabolic.org
Clenbuterol is effective,but it also has risks.Personally,I wouldn't want to use it.

There's also some very interesting information about the regulation of Myostatin during exercise and how Clenbuterol affects it.Take Clenbuterol long enough and it raises myostatin.Not a good thing.
The Myostatin issue brings up a fascinating point.Myostatin works like a brake on gaining muscle.
One of the most amazing conditions that exists in the world of muscle is Myostatin-related Muscle Hypertrophy.The animals that have this gene knocking out myostatin are pretty damn freaky looking.

 

A Myostatin deficient Bull

So in the simplest terms;turn down the myostatin and turn up the muscle.This condition has happened to rare humans as well.It may very well be one of the reasons some humans have a major natural advantage in gaining muscle mass.Of course I'm sure that all gets very complicated,and speculative.But lowering the impact of myostatin on your muscles is an exciting idea as a bodybuilder.Now the question is can it be done? There are a number of products that have claimed they can lower myostatin dramatically.So far they look like a bunch of cow manure.You can't take a magic pill.
It has been done experimentally to lab mice by gene editing.That's not something you can put in a supplement.But you may be able to improve the situation by taking Creatine and Vitamin D.
From the MD article;

Certain nutritional supplements are known to inhibit myostatin. Therefore, consuming them should negate myostatin’s hold on muscle growth directly induced by clenbuterol. Creatine is a well-characterized compound that has been unmistakably shown to enhance muscle size and strength. In addition to creatine’s obvious function as a primary energy storage molecule used to regenerate muscle ATP, thus prolonging muscle function, creatine has also been shown to stimulate muscle growth.⁴ More recently, however, a study by Saremi et al.⁵ demonstrated that creatine consumption causes a decrease in myostatin levels in muscle cells, leading to significant muscle growth. In this study, two groups of men performed resistance training with or without creatine for a total of eight weeks. Both groups showed decreased levels of myostatin, but the group that performed resistance training and consumed creatine had a considerably larger decrease in myostatin levels along with greater gains in muscle mass and strength— clearly demonstrating the ability of creatine to reduce myostatin levels, improving muscle growth and strength.
Another potent myostatin inhibitor is vitamin D. As shown in a recent study by Garcia et al.⁶, vitamin D exposure decreased the amount of myostatin found in isolated muscle cells, generating greater muscle growth. In addition to the decrease in myostatin, this study also showed that vitamin D triggers an increase in the powerful inhibitor of myostatin known as follistatin, which increases muscle mass by inhibiting myostatin.⁷ Ultimately, this study indicates that the decrease in myostatin level and activity caused by vitamin D significantly increased muscle fiber size.

Creatine Monohydrate and Vitamin D are easy safe additions to any lifters supplements.I'm sure most amateur bodybuilders take creatine sometimes.But vitamin D levels may not be considered.That's a mistake because vitamin D is important for over all health.
Dr Rhonda Patrick has a great video about the target range for vitamin D and it's benefits.

Vitamin D 
is actually a secosteroid and usually taken as a supplement in the form of D3.
You can of course get it foods,and from sunlight as well.
If you are going to take it as a supplement it might be best to take it with a meal containing green vegetables rich in Vitamin K,and K2.That will help the vitamin D take calcium into your bones rather than depositing it in your soft tissues where it may damage your arteries.
But do please research this for yourself when making any decisions about what supplements to take.After all I'm just some nobody on the internet :)

Keeping your myostatin levels down could have a positive impact on muscle growth over time.If you're trying to build muscle without taking AAS,and other drugs,that could be a real plus.

I'll leave you with a talk from a real hardcore lifter, Stan Efferding, who does believe in the benefits of Vitamin D.