In addition to the nervous system, muscles, i.e. movement activity is controlled by the hormonal system. Hormones are produced in endocrine glands from which they are transported through blood to the target cells. The releasing of hormones from a number of target glands is affected by the adenohypophysis. Hormones produced by the neurohyphysis include e.g. antidiuretic hormone (ADH) which decreases the production of urine. Besides other functions growth hormone (GH) is responsible for growth of the muscle mass. The presence of glucose in the blood referred to as glycemia is maintained by insulin and glucagon. Insulin transports the glucose to cells (during a movement activity especially into muscle cells) and thus reduces the blood glucose level. Glucagon, however, has the opposite, effect; it increases the blood glucose level. These hormones are released from the pancreas. During exercise the insulin level decreases in proportion with the intensity of the aerobic work. During an anaerobic activity the insulin production tends to rise.
During exercise epinephrine (adrenaline) and norepinephrine (noradrenaline) are released from the adrenal medulla into the blood. They transport energy to muscles and enhance the activity of the heart and other organs promoting muscle contraction.
In connection to adaptation of an organism to training at higher altitudes we need to mention erythropoietin which controls red blood cell production.
Testosterone, the principal male sex hormone, has anabolic effects and enhances protein biosynthesis. Through protein stimulation it reinforces bone production and growth of muscle tissue.
The last two mentioned hormones are often abused as doping substances in sports.