CHAPTER 22

The Endocrine System

“The main effects of growth hormone are stimulation of bone growth, anabolic effect in the muscles, conservation of protein and carbohydrates, and lipolysis, i.e. mobilization of fat for energy.”

– Ori Hofmekler, MuscleMag International contributor

The endocrine system works with the nervous system to maintain the body’s internal balance. It is, in other words, a regulatory system. Regulation can take two forms: monitoring and adjusting internal physiological mechanisms, and adapting the body to external stimuli. The endocrine system carries out these important functions by use of chemical messengers called hormones. By definition a hormone is a chemical substance that is produced in one part of the body and travels by way of the bloodstream to another area where it carries out its action. Bodybuilders will be interested to know that hormones are either protein or steroid in nature.

Hormone production and release are controlled by various parts of the brain. Among these areas are the hypothalamus, and anterior and posterior pituitaries. These activation centers stimulate the various endocrine glands that are located throughout the body. Everything from excretion to digestion to sleep and sex drive is controlled by hormones. For the purposes of this book it’s not necessary to go into great detail. To give the reader a basic understanding of endocrinology (the study of hormones), I shall look at one hormone, testosterone, and its implications for bodybuilders.

Testosterone is produced by the testes of sexually mature males. It’s often called “the male hormone,” but this term is misleading as females also have testosterone circulating in their bodies. Conversely, the hormone estrogen, often referred to as “the female hormone,” is also found in males. It’s the relative concentrations of both that have given rise to the descriptions male and female.

Testosterone and estrogen are present in both men and women – it’s the relative amounts that differentiate “male” and “female.”
Photo of Elle Patille and Larry Vinette by Paul Buceta

Through a number of intermediate steps, testosterone is produced from the precursor, cholesterol. (Yes, there is a use for it after all, but don’t consciously try to include it in your diet as you will get all you need, even if you cut down on high-cholesterol food.)

Testosterone has numerous functions, among which are deepening of the voice, growth of pubic hair, increased muscle size and strength, and sperm production. This is the hormone that causes males to be, on average, larger and stronger than females. Even among males there is much variation. Ectomorphs tend to have low levels and are usually underweight, timid and nervous. Nervousness could possibly reduce testosterone levels, so it’s difficult to say which is the cause and which is the effect.

Mesomorphs have bloodstreams loaded with testosterone. The result – low bodyfat level, a skeleton covered with muscle (or great potential for it), and a tendency towards increased aggression. The high levels of circulating hormone produce rapid muscular weight gains, and at the same time keep bodyfat percentage to a minimum.

Endomorphs fall somewhere in between. They have good muscle size, but they are also inclined to carry excess fat. The most recent research suggests that regular exercise (including bodybuilding) increases the production of testosterone. Naturally there is an upper limit. Train too hard for too long and you’ll overtax the body’s recovery system. To combat stress, the body reduces testosterone production and increases cortisol production. Cortisol has the opposite effect of testosterone, as it reduces muscle mass. This is why I keep stressing the perils of overtraining throughout the book.

Photo of Gunter Schlierkamp, Dexter Jackson and Jay Cutler by Raymond Cassar