Testosterone Facts - definition of anabolic steroids

The traditional definition of anabolic steroids is that these molecules are synthetic derivatives of the natural male sex steroid hormone, testosterone (1). This definition is only partially true. Anabolic steroids are syntethic derivatives or analogs of testosterone, but testosterone is not a male sex hormone. Therefore, in order to accurately define anabolic steroids, it is important to describe what testosterone is and what basic influences it has on body functions.

Facts about Testosterone

Testosterone is produced by both sexes

Testosterone is a steroid hormone that is produced by specific glands in boths sexes. It influences or regulates both sexually related and non-sexually related mechanisms. Testosterone exhibits these influences by binding to receptors in several tissues of the body. Receptors for testosterone are located in the brain, heart, lungs, muscles, bones, skin, sexual organs, and other tissues and organs.

Testosterone is a steroid

Testosterone is classified as a steroid due to its molecular structure. A steroid is any chemical that posseses the specific four-ring molecular structure. The four rings of a steroid molecule are designated as either the A, B, C or D ring and each of the carbon atoms numbered. Utilizing this naming system, testosterone's chemical name is 17-beta-hydroxyandrost-4-en-3-one.

The human body produces dozens of different steroids. Examples of steroids that are made by both sexes include estradiol, progesterone and testosterone. Notice the similarity in the molecular structures of the major sex steroids: testosterone, estrogen and progesterone.

Testosterone is an androgen

An androgen is defined as a sex hormone that is produced by the gonads (testicles or ovaries) and adrenal glands and posseses the capability of inducing male characteristics. Testosterone meets these criteria in the male. However, under normal physiologic conditions, the amount of testosterone produced by these glands in the female does not include male characteristics. In exceptionally large doses, testosterone does produce male characteristics in women. This can be seen in women bodybuilders. Examples of other physiologic androgens common to both men and women are dihydrotestosterone (DHT), dehydroepiandrosterone (DHEA), and androstenedione ("andro").

Testosterone is a hormone

A hormone is defined as a substance that is produced by an endocrine gland and regulates metabolism, growth, and reproduction through specific chemical processes within the body. Hormones also serve to coordinate the function of various groups of organs. Hormones that have the molecularstructure of a steroid are called steroids hormones. Not all hormones are steroids, that is, they do not have the specific four-ring structure that defines a steroid. Examples of non-steroid homnrones are peptide and poly-peptide hormones.

Testosterone is an Anabolic Steroid

Testosterone causes considerable anabolic or "building" effects on the body. Its anabolic influences are due to its ability to bind to receptors contained in many tissues throughout the body. Some examples of testosterone's anabolic effects are listed below.

In skeletal muscle tissue, testosterone binds to receptors within the cytoplasm of the muscle cells. The testosterone/receptor complex enters the muscle cell nucleus and stimulates genetic material to begin the process of protein synthesis within muscles cells. Prolonged protein synthesis can result in enhanced muscle mass and strength, especially when combined with athletic and weight training.

In bone tissue, testosterone binds to receptors within osteoblasts (bone-forming cells). The osteoblast is stimulated to incorporate calcium and other proteins to form new bone tissue. This increases bone mineral density and strength of bones.

In red blood cells, testosterone binding results in an increased hemoglobin concentration. It also works synergistically with erythropoietin to increase red blood cell formation and total blood volume.

Testosterone has Anabolic and Androgenic Properties

Several body functions are under either direct or indirect control of testosterone. It has a direct stimulatory effect on a number of tissues and organs, including skeletal muscle, bone, visceral organs, stem cells, and the immune system. Within the brain, testosterone acts as a direct and indirect neurotransmitter to influence behavior, including the enhacement of libido in both men and women. Testosterone also affects secondary sexual characteristics.

References:
1. Anabolic steroids and the athlete By William N. Taylor