All About Endocrine Hormones

When you say hormones, you may be thinking of estrogen and testosterone. But these complex chemicals govern far more than sexuality.

Hormones, which are chemical signals, affect growth, metabolism, blood pressure, even behavior. When our hormones don't behave, we may not either.

The majority of hormones that affect the body's processes are produced by the endocrine glands. These glands release hormones directly into the blood or lymph system. The hormones travel in the blood to tissues and organs where they can attach to specific cell sites called receptors. By attaching to receptors, hormones trigger various responses in the tissues.

Endocrine glands

These are the endocrine glands:

Pineal gland. It secretes melatonin, which affects reproductive development and the daily sleep/wake cycle.
Pituitary gland. It makes hormones that control other endocrine glands.
Thyroid gland. It makes a hormone that controls the rate of metabolism (the rate cells burn fuels from food to make energy).
Parathyroid glands. These make a hormone that, along with a hormone from the thyroid (calcitonin), regulates the level of calcium in the blood.
Thymus gland. It produces thymosin, which plays an important role in the development of the body's immune system.
Adrenal glands. These produce several hormones. They help regulate salt and water balance in the body, increase blood pressure and heart rate, and play a part in the immune system and in sexual development.
Pancreas. This produces insulin and glucagon to regulate the level of sugar carried in blood.
Ovaries. These secrete the female hormones estrogen and progesterone.
Testes. These secrete male hormones called androgens, including testosterone.

Other areas of the body produce hormones. The lining of the stomach produces a hormone called gastrin, which causes the release of enzymes used to digest food. Special cells in the wall of the upper chambers of the heart, called atria, produce atrial natriuretic hormone, or atriopeptin. During pregnancy, the placenta secretes human chorionic gonadotropin, which signals the mother's ovaries to secrete hormones to maintain the pregnancy.

Important hormones

Humans have about 100 known hormones. Here are some of the more important hormones:

Growth hormone, one of many hormones secreted by the pea-sized pituitary at the base of the brain. It stimulates the growth of bones, muscles and other organs. Underproduction stunts growth, and may contribute to depression and sluggishness. Experts debate the pros and cons of growth hormone replacement therapy.
Insulin, manufactured by the pancreas, regulates our body's blood sugar. Lack of insulin or the inability to process it causes diabetes, which can be treated by diet, oral drugs, or insulin.
Thyroid hormone, from the thyroid gland in the neck, regulates metabolism, growth, and development. Deficiencies cause weight gain and sluggishness, which doctors treat with synthetic thyroid hormone replacement. Overproduction causes weight loss, rapid heartbeat, and anxiety. That can be treated by surgically removing the gland, by chemotherapy, or by radiation.
Adrenaline, or epinephrine, regulates blood pressure and heart rate. It comes from the adrenal glands above each kidney.
Cortisol, another adrenal product, plays an important role in metabolism.

Without a doubt, the most talked-about hormones deal with sex. Not only are they important in sexual development and reproduction, they also affect behavior and define male and female characteristics. The loss of estrogen during menopause can cause depression and loss of energy and can also weaken bones and increase risks of heart attack and stroke.

Experts generally agree hormone therapy can help relieve menopausal symptoms and help prevent osteoporosis. However, hormone replacement therapy also carries increased risks, so its use should be individualized. Some men may also experience midlife changes from decreased production of testosterone.