Student Handout

It’s fairly common knowledge that exercising a muscle makes the muscle grow and become stronger. However, athletes in the US as well as in many other countries try to enhance their muscle performance even more by using steroids. Similarly, body builders use steroids to make their muscles grow beyond the size that would be produced naturally by lifting weights. How does this actually happen, and what are the consequences?

Let’s explore the biology of steroids. Steroids are compounds that are synthesized in the body from the precursor, cholesterol. Some steroids are made in the adrenal glands (near the kidney) and some are made in the sex glands of both males and females.

1. Give an example of a steroid found in the adrenal glands and in the male and female sex glands.

2. Which of these steroids is used by athletes and by body builders?

3. What is an anabolic steroid?

Although anabolic steroids are used to increase muscle growth (and enhance performance), they do a lot of other things in the body as well. In fact, all anabolic steroids have androgenic properties, despite claims to the contrary. For this reason, they are termed anabolic-androgenic steroids or AAS, although most people just say “anabolic steroids” as a shortcut.

4. What is an androgen?

5. List 3 common androgenic effects of anabolic steroids in the body.

When athletes use anabolic steroids to enhance their performance, they don’t just take a pill or an injection before the race or before the game. They must use the drug over a period of time in order to obtain the muscle growth. To understand why this is the case, we need to know how steroids actually make the muscles grow. First, after taking an anabolic steroid (by mouth or by injection), the steroid enters the bloodstream and travels to all tissues in the body (see Module 1). Most anabolic steroids are very lipophilic, and therefore, they can cross cell membranes easily to reach the inside of all cells.

6. Define “lipophilic.” What characteristic of the steroid structure makes it lipophilic?

7. Why can a lipophilic steroid cross cell membranes so easily?

Once inside the cell, the steroid binds to a special protein called a steroid receptor. In this case we are referring to the “androgen receptor.” The complex containing the anabolic-androgenic steroid and its receptor then travels through the cytoplasm and crosses the nuclear membrane to enter the nucleus.

8. How does a big, bulky molecule consisting of a steroid and a protein get across a nuclear membrane?

Once in the nucleus, the steroid receptor complex comes into contact with the DNA. The steroid receptor binds to a specific site on the DNA molecule, causing the DNA to start the process of gene transcription. This leads to the synthesis of certain proteins, depending on the cell-type and the part of the DNA to which the steroid receptor complex binds. All of these events take time, and a sustained use of the steroid is required to continually instruct the genes to synthesize more protein.

9. What kind of molecule is DNA? Describe its essential features.

10. What is gene transcription?

11. How is the protein synthesized?

The cell-type that contains the androgen receptor will define the kind of protein that is synthesized. For example, in the case of the muscle cell, the anabolic steroid will stimulate the synthesis of certain types of muscle fiber proteins.

12. In what type of cells would anabolic-androgenic steroids act to cause:
-the growth of chest hair
-emotional disturbances such as aggression

As more muscle fiber proteins are produced, the muscle gets bigger and more powerful. But once the athlete or body builder stops taking the steroids, their muscles slowly revert to their normal size.

13. Draw a muscle cell. Label the essential structures in the muscle cell that help it to contract. Which muscle proteins constitute the muscle fibers?

The use of the steroids provides an unfair advantage over non-drug using athletes. So steroids have been banned from use in local, national and international competition. Despite this rule, many athletes continue to use steroids until shortly before a competition, when they hope that a drug test will not detect it. In many cases, this plan doesn’t work. The drug is still present in their bodies long after the athlete stops taking it. This is due to the lipophilic character of the steroid.

Lipophilic compounds are difficult to eliminate from the body (the same is true for THC, found in marijuana). Normally, drugs are eliminated by the liver and the kidney. Enzymes in the liver convert (metabolize) drugs into a more water-soluble (polar) form. Once the drug is in a more water-soluble form, it travels through the bloodstream to the kidney, where it is collected in the urine and eliminated from the body. But in the case of highly lipophilic drugs such as anabolic steroids, they are metabolized very slowly so that only small amounts of drug are eliminated over time.

14. Why is it so difficult for an anabolic steroid to be metabolized by the liver enzymes?

15. Why is it so difficult for an anabolic steroid to be retained by the kidney where it would be eliminated in the urine?

If the lipophilic steroid can’t be metabolized easily nor retained by the kidney, then it re-enters the bloodsteam to circulate throughout the body. However, it does like to “hide” in cells that contain a lot of lipids, such as fat cells. With continued use, the anabolic steroid starts to accumulate in the fat cells.

16. If the athlete stops using the steroid, the amount of steroid in the blood starts to decrease. What would account for the initial decrease of steroid in the blood?

17. Although the steroid decreases in the blood, it doesn’t disappear right away. Instead, there is a steady low-level amount of steroid that is present in the blood over a long period of time (and thus the positive drug test). Where is the steroid coming from? What is the major force moving it into the bloodstream?

The ban on steroid use in sports is not based solely on the unfairness issue. There are serious health consequences that can occur from long-term steroid use.

18. List 3 additional health consequences from the repeated use of anabolic steroids.