Hormones are really important to bone strength. Hormones are chemicals made by glands that travel throughout the body and have many effects on growth, maturation, energy, weight, and bone strength. Sex hormones (estrogen made in the ovary of females and testosterone made by the testes in males) control ability to reproduce. They also are a major reason that bone strength increases in the early teenage years. When teenagers have low estrogen or testosterone levels, the bone becomes weaker.
Other hormones come from the thyroid gland, the parathyroid gland, the pituitary gland near the brain, and the brain itself. These hormones control levels of calcium in the blood, energy levels, and ability to grow. They act the same in boys and in girls. Healthy bones need the correct levels of all of these hormones. There are many reasons these hormones can be too high or low, but fortunately they are all uncommon.
Most of these hormones do not become abnormal because of things we can do. Estrogen and testosterone, however, depend on normal body weight. If teenagers do not get enough nutrition and become too thin, then the hormone levels will be too low. The parathryoid hormone also responds to nutrition. Too little calcium causes parathyroid hormone to increase and that will dissolve some of the bone.
The next section is about weight