Exercise elevates multiple hormone levels, most of them beneficial. The type, duration and intensity of exercise plays a role in not only the hormones that get stimulated, but the degree of stimulation that occurs. Intense resistance training produces a vastly different effect than marathon training. Consult a health-care practitioner before beginning any strength-training program.

Testosterone

Testosterone — the hormone primarily responsible for muscle growth — is stimulated as a direct result of the intensity of your exercise. The harder you train, the more muscle you break down. In response, your body signals your endocrine system to produce more testosterone. Resistance training has been shown to stimulate a greater testosterone response than endurance training, according to a 2004 study published in the "Journal of Applied Physiology." This response occurs in both men and women, but, because men produce more testosterone than women, is more pronounced in men, according to a 1991 study in the "International Journal of Sports Medicine."

Insulin

Your insulin levels rise during training, and this is directly proportional to both your training intensity and volume. The longer and harder you train, the more your body scavenges glycogen, or usable sugar, from both your blood and muscles. The greater the intensity, the greater your sensitivity to sugars following a workout, as your insulin levels are higher. Training with prolonged intensity will show a marked increase in insulin response according to a 1996 study published in "Diabetes Care." This increase makes it easier to metabolize any sugars you consume immediately after your workout.

Thyroid

Your body produces various thyroid hormones, which help your body produce energy. This production is the result of thyroid hormones scavenging fat, sugar and amino acids for energy. The longer you train, the more thyroid hormone you generate. This increase does not specifically allow you to burn more fat, as thyroid hormones cannibalize everything for energy, including lean muscle tissue. Intense aerobic exercise sustained over time generates the greatest thyroid response, according to a 2005 study in "Neuro Endocrinology Letters."

Growth Hormone

Growth hormone assists with many functions — fat loss, muscle growth, skeletal development and the health of your joints. Growth hormone is produced in response to both the intensity and duration of exercise. The longer and harder you train, the more growth hormone you will produce. Limits to this production do exist, so endless training does not result in an endless supply of growth hormone. Both genders experience a growth hormone response to training, and the greatest response is shown through high intensity training, according to a 2005 study in "Sports Medicine."