Biology
Human Being: The Endocrine System
The hormones produced by endocrine glands pass directly into the blood. They have no excretory duct.
| Gland | Hormone | Effect |
|---|---|---|
| Pituitary | growth hormone | growth |
| Thyroid | thyroxine | metabolism |
| Adrenal | adrenaline | stress |
| Pancreas | insulin | lowers blood sugar |
- The pituitary gland is located at the base of the brain and is called the "master gland". It produces growth hormone.
- The thyroid gland produces the hormone thyroxine, which contains iodine.
- The adrenal glands: adrenaline, the stress hormone.
- The pancreas is a mixed gland. Insulin lowers, glucagon raises the blood sugar level. It also produces digestive juice.
- The gonads (sex glands) are also mixed glands.
Key facts
- Growth hormone: too much in childhood causes gigantism; too little growth hormone causes dwarfism (nanism). Too much in adults causes acromegaly.
- Too little thyroxine: cretinism in children, myxedema in adults. Too much: Graves' disease (Basedow's disease).
- Insufficient insulin causes diabetes mellitus. Iodine deficiency causes goiter (endemic).
- Glands with mixed secretion: the pancreas and the gonads.
- Hormones act in small amounts, have high activity, and have a range of action (target organ).