Insulin as doping agent

Insulin is a hormone produced in the Beta cells of the pancreas, medically it is primarily used to treat insulin deficient individuals (diabetic patients) with diabetes mellitus type 1.

Insulin has been increasingly used as a doping agent, among the different actions of insulin are protein anabolism, increased glucose uptake and glycogen storage in the muscles, net amino acid uptake and reduced muscle protein breakdown.

As performance in many different sports is highly related to the glycogen stores within the muscles, this is one of the main reasons for the use of insulin as a doping agent.

Insulin is also useful as a synergistic agent with anabolic steroids, as steroids increase muscular mass and strength and insulin inhibits the catabolism of this muscle.

Insulin is used simultaneously with glucose, with aim to increase the entry of glycogen and amino acids to the muscle, a technique called hyperinsulinaemic clamp.

The combination of insulin and high carbohydrate diets has also an anabolic effect on muscle mass through the inhibition of protein breakdown.

It is considered that may be up to 10% of bodybuilders use insulin.

Insulin has a half-life of 4 minutes in the body so a detection in doping tests is really difficult, and if detected, it is really hard to differentiate endogenous insulin from external insulin.

The most common adverse effect is, as expected, hypoglycemia, with up to 57% of users reporting to have experienced at least one event, but other complications include loss of consciousness, coma and death.

Another side effect reported in diabetic patients is weigth gain, though this is probably not a problem in training regimens as the strict diets and separated doses make this very unlikely.

There are different presentations of insulin, but rapid acting insulins (Novolog, Humalog, humilin-R) are the most frequently used for physique performance, injected subcutaneously, and used immediately after work-out, with doses of 1IU for every 7-10kg of lean body weigth approximately, with a full dose of 10UI usually combined with an ingestion of at least 100gr of simple carbohydrates about 10-30 minutes after the injection.

It is recommended that bodybuilders pretending to use insulin should read a more comprehensive guideline elsewhere.

Bibliography

1-. Intern Med J. 2015 Mar;45(3):239-48. doi: 10.1111/imj.12629. Doping in sport: effects, harm and misconceptions. Birzniece V.
2-. Fundam Clin Pharmacol. 2011 Oct;25(5):535-63. doi: 10.1111/j.1472-8206.2010.00881.x. Epub 2010 Oct 6. Doping and musculoskeletal system: short-term and long-lasting effects of doping agents. Nikolopoulos DD, Spiliopoulou C, Theocharis SE.
3-. William Llewellyn. Anabolics, 10th ed. Molecular Nutrition, 2010.