secrete the chemical substances called hormones. Endocrine glands are ductless glands - that is, they secrete the hormones directly into the blood and not into ducts. For instance, the pancreas secretes the hormone insulin into the blood, which then delivers the insulin to cells throughout the body.
a collection of specialized cells that is located in the lower central part of the brain, is the main link between the endocrine and nervous systems. Nerve cells in the hypothalamus control the pituitary gland by producing chemicals that either stimulate or suppress hormone secretions from the pituitary.
Although it is no bigger than a pea, the pituitary gland, located at the base of the brain just beneath the hypothalamus, is considered the most important part of the endocrine system. It's often called the "master gland" because it makes hormones that control several other endocrine glands.
The thyroid, located in the front part of the lower neck, is shaped like a bow tie or butterfly and produces the thyroid hormones thyroxine (pronounced: thy-rahk-sin) and triiodothyronine (pronounced: try-eye-oh-doe-thy-ruh-neen). These hormones control the rate at which cells burn fuels from food to produce energy.
Attached to the thyroid are four tiny glands that function together called the parathyroids. They release parathyroid hormone, which regulates the level of calcium in the blood with the help of calcitonin , which is produced in the thyroid.
The body also has two triangular adrenal glands, one on top of each kidney.
The adrenal glands have two parts, each of which produces a set of hormones and has a different function:
The outer part, the adrenal cortex, produces hormones called corticosteroids that influence or regulate salt and water balance in the body, the body's response to stress, metabolism, the immune system, and sexual development and function.
The inner part, the adrenal medulla, produces catecholamines, such as epinephrine. Also called adrenaline, epinephrine increases blood pressure and heart rate when the body experiences stress.
The pineal body, also called the pineal gland, is located in the middle of the brain. It secretes melatonin, a hormone that may help regulate when you sleep at night and when you wake in the morning.
The gonads are the main source of sex hormones. Most people don't realize it, but both guys and girls have gonads.
In guys the male gonads, or testes, are located in the scrotum. They secrete hormones called androgens, the most important of which is testosterone. These hormones tell a guy's body when it's time to make the changes associated with puberty, like penis and height growth, deepening voice, and growth in facial and pubic hair. Working with hormones from the pituitary gland, testosterone also tells a guy's body when it's time to produce sperm in the testes.
A girl's gonads, the ovaries, are located in her pelvis. They produce eggs and secrete the female hormones estrogen and progesterone . Estrogen is involved when a girl begins to go through puberty. During puberty, a girl will experience breast growth, will begin to accumulate body fat around the hips and thighs, and will have a growth spurt. Estrogen and progesterone are also involved in the regulation of a girl's menstrual cycle. These hormones also play a role in pregnancy.
The pancreas ( is also part of the body's hormone-secreting system, even though it is also associated with the digestive system because it produces and secretes digestive enzymes. The pancreas produces (in addition to others) two important hormones, insulin and glucagon. They work together to maintain a steady level of glucose, or sugar, in the blood and to keep the body supplied with fuel to produce and maintain stores of energy.
Type 1 Diabetes
When the pancreas fails to produce enough insulin, type 1 diabetes occurs. In kids and teens, type 1 diabetes is usually an autoimmune disorder, which means that some parts of the body's immune system attack and destroy the cells of the pancreas that produce insulin. To control their blood sugar levels and reduce the risk of developing diabetes problems, kids and teens with this condition need regular injections of insulin.
Type 2 Diabetes
Unlike type 1 diabetes, in which the body can't produce normal amounts of insulin, in type 2 diabetes the body can't respond to insulin normally. Kids and teens with the condition tend to be overweight. Some kids and teens can control their blood sugar level with dietary changes, exercise, and oral medications, but many will need to take insulin injections like people with type 1 diabetes.
Why does an iodine-deficient diet cause the thyroid gland to enlarge? In an iodine -deficient state, the amountof T3 and T4 production decreases because iodine is necessary for the synthesis of the thyroid hormones. With insufficient iodine, thyroid hormones cannot be made in quantities great enough to shut off the secretion of TSH through negative feedback. Persistent stimulation of the thyroid gland by TSH causes the thyroid gland to enlarge; an enlarged thyroid gland is called a goiter.
Gigantism is abnormally large growth due to an excess of growth hormone during childhood, before the bone growth plates have closed.