Introduction to Hormones

Hormones are powerful biological signals which help to integrate the various organ systems in the body. Often the effect of a hormone can be seen with a hormone imbalance. There are interactions of various hormone systems, and the hormone secretion in a gland is often regulated tightly by a stimulating hormone, such as with the follicle stimulating hormone or the thyroid stimulating hormone. Such feedback systems are operational in the hypothalamus/pituitary/hormone gland systems.

The adrenal glands, thyroid gland, ovaries and testicles are all examples of such feed back loop systems. For instance, if the thyroid gland does not produce enough thyroid hormone, the hypothalamus will send more thyrotropin-releasing hormone(TRH) to the anterior pituitary gland. There thyroid stimulating hormone(TSH) is being formed at a higher rate, which in turn will stimulate the thyroid gland to produce T3 and T4 thyroid hormones. The presence of circulating thyroid hormones is being recognized by the hypothalamus and a reduced amount of TRH is secreted by the hypothalamus.

Such negative feedback loops are very useful to automatically adapt our hormone production to the changing needs throughout a day. This ensures that the hormone balance is maintained within the body. Similar feedback loops are in place between the gonads and the hypothalamus/pituitary gland and with growth hormone production. Apart from the releasing hormones in the hypothalamus there are many neuropeptides, called neuronal transmitters, such as serotonine, dopamine, acetylcholine and many others, which are operational within the central nervous system and the rest of the body. They are transmitting nerve signals in the nervous system and the vegetative nervous system (sympathetic and parasympathetic nervous systems). The table below lists some of the important hormones in the body and their actions:

*Some hormones and their actions*
Name of hormone:	Description of hormone actions:
thyroid hormone	increases protein synthesis and oxygen consumption of every cell in the body
ACTH (=corticotropin or adrenocorticotropic hormone)	helps you to cope with stress by stimulating cortisol production in the adrenal gland
growth hormone	promotes growth in younger years; in adults important metabolic stabilizer, maintains blood glucose levels in periods of fasting
ADH (=antidiuretic hormone or vasopressin)	promotes water conservation in the kidney; without it diabetes insipidus occurs
cortisol	helps maintain blood pressure and cardiac output in response to stress; stimulates glucose production from protein
aldosterone	causes sodium retention and potassium loss by the kidneys; renin stimulates release of it thus helping to maintain blood pressure
Epinephrine (=adrenaline)	raises blood pressure, makes the heart beat faster, opens up small bronchial tubes and increases the blood sugar level
estrogens	stimulates ovaries, lubricates the vagina, builts up lining in uterus, stimulates breast growth and female body built
testosterone	responsible for male body built and muscle power, stimulates sex drive
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Finally, there is the ecosanoid system, which works on a cellular level (tissue hormones).

You may have heard of the prostaglandins, the leukotrienes, lipoxins and others. They are all various ecosanoids that have anti-inflammatory, immune stimulating or artery hardening effects in the body. Dr. Barry Sears describes in chapter 16 of his book (Ref.1) the details of the ecosanoid metabolism. Other authors have also described the "syndrome X", which is now called the "syndrome of insulin resistance" or is also known among physicians as "hyperinsulinism". In diseases such as diabetes the chronically elevated blood sugar and the elevated insulin level lead to accelerated hardening of the arteries (atherosclerosis) as is pointed out in Ref. 2. The biochemistry of elevated insulin levels is now more fully appreciated by physicians as the cause of arthritis, cancer, heart attacks and strokes.

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Hormones

Disclaimer:

This outline is only a teaching aid to patients and should stimulate you to ask the right questions when seeing your doctor. However, the responsibility of treatment stays in the hands of your doctor and you.

References:

1. B. Sears: "The age-free zone". Regan Books, Harper Collins, 2000.

2. R.A. Vogel: Clin Cardiol 20(1997): 426-432.

3. The Merck Manual, 7th edition, by M. H. Beers et al., Whitehouse Station, N.J., 1999. Chapter 8: Thyroid disorders.

4. The Merck Manual, 7th edition, by M. H. Beers et al., Whitehouse Station, N.J., 1999. Chapter 7:Pituitary disorders.

5. J Levron et al.: Fertil Steril 2000 Nov;74(5):925-929.

6. AJ Patwardhan et. al.: Neurology 2000 Jun 27;54(12):2218-2223.

7. ME Flett et al.: Br J Surg 1999 Oct;86(10):1280-1283.

8. The Merck Manual, 7th edition, by M. H. Beers et al., Whitehouse Station, N.J., 1999. Chapter 261: Congenital anomalies.

9. AC Hackney : Curr Pharm Des 2001 Mar;7(4):261-273.

10. JA Tash et al. : Urology 2000 Oct 1;56(4):669.

11. D Prandstraller et al.: Pediatr Cardiol 1999 Mar-Apr;20(2):108-112.

12. B. Sears: "Zone perfect meals in minutes". Regan Books, Harper Collins, 1997.

13. J Bain: Can Fam Physician 2001 Jan;47:91-97.

Last Modified: Dec. 19, 2007