Hormones

Hormones are chemicals made by the body that transport messages from one cell to another. Hormones usually travel in the blood.

Chemical structure of epinephrine, a key hormone in the body. Source: Wikimedia Commons.

Types

There are many types of hormones in the body. Examples of hormones include the following:

• Sex hormones
  • Estradiol
  • Progesterone
  • Testosterone

• Hormones stimulating other hormones (tropic hormones)
  • Gonadotropin Releasing Hormone
  • Thyroid Stimulating Hormone

• Other hormones
  • Cortisol
  • Dopamine
  • Epinephrine
  • Growth Hormone
  • Insulin
  • Melatonin
  • Oxytocin
  • Relaxin
  • Serotonin

Description

The body makes hormones to send messages to its cells. Hormones are amino acids, peptides, proteins, or lipids.

Role of Hormones in the Body

Hormones are part of the endocrine system. They help various parts of the body communicate and send feedback to each other so that the body functions properly.

Hormones control numerous functions in the body, including growth, metabolism, puberty, mood, the immune system, and reproduction.

How Hormones Work

Location of the hypothalamus in the brain. Source: Wikimedia Commons.

Certain parts of the body release hormones in response to certain stimuli. For example, the hypothalamus secretes hormones (such as gonadotropin releasing hormone—GnRH) that stimulate the release of many other hormones (such as follicle stimulating hormone—FSH). When the end hormone levels (such as FSH) are high, the hypothalamus is turned off from producing more stimulating hormones (such as GnRH).

Other organs, such as the parathyroid gland, secrete hormones in response to local conditions, such as calcium levels in the blood.

Cells have receptors for hormones, which are places where the hormone binds. When the hormone binds here, changes occur inside the cell that lead to the change the hormone was designed to create.

Diseases Involving Hormones

Some diseases involving abnormalities in the production or action of hormones include the following:

• Addison Disease
• Cushing Disease
• Diabetes

Related Professions

• An endocrinologist is a medical doctor (MD) who has completed an internal medicine residency and specialized training in endocrinology, the study of the hormonal systems of the body.

History

How hormones were discovered

The study of endocrinology began when German scientist Arnold Adolph Berthold noted that castrated roosters did not develop combs or exhibit overtly male behavior. He found that replacement of testes back into the abdominal cavity of the same bird or another castrated bird resulted in normal behavioral and morphological development. It was not proven that the testes released a substance that engenders male characteristics until it was shown that the extract of testes could replace their function in castrated animals.^[1]

How hormones were named

The word hormone originates from Greek hormōn, present participle of horman, meaning to stir up and from hormē, meaning impulse, assault. It's been in use since 1905.^[2]

Research

An area of recent interest is the study of hormone hungers. One of these is ghrelin, a hormone secreted in the stomach, small intestine, and colon, that regulates appetite, energy, and the use of glucose by the body.^[3]

References

1. ↑ Wikipedia. Endocrinology.
2. ↑ Merriam-Webster Online. Hormone.
3. ↑ Tritos NA, Kokkotou EG. The physiology and potential clinical applications of ghrelin, a novel peptide hormone. Mayo Clin Proc. 2006 May;81(5):653-60. PMID 16706263

External Links

Society for Endocrinology