Hormones

[gene]

I know that a hormone is a chemical substance transported in the body via the bloodstream.

 

If we compare the hormone to enzymes, we know what enzymes are made up of, and that they do not alter in a chemical reactiona and can only be destroyed by heat or ph.

 

SO, my question is what exactly do you define "chemical substance" and do hormones get destroyed or do like "die"? Plus, is there any specific structures that a hormone holds?

[Xavier]

Hello,

 

'Hormone' is one of those terms, like 'vitamin' that was brought into being before the science was mature in order to explain (or at least name) a series of groups of conditions or symptoms that shared traits in common (i.e. activity/trauma at one body site affecting another apparently unconnected site and the modes of failure of these traits by both 'disconnection' or uncontrolled activity).

Clinicians were getting to grips with a bodies negative feedback and homeostasis systems long before there was any possibility of them directly detecting the hormone molecules themselves. The existence of the hormones was theorised from their effects and their sites of production and action discovered by piecing together clusters of symptoms seen in all the many rare tumours and congenital defects.

 

It turned out that hormones are a disparate bunch of substances, chemically. Some are peptides, usually under a hundred base pairs long, such as parathyroid hormone [PTH] and Growth hormone [GH]. They typically have a half life up to a few days in the blood stream so cannot respond to rapid environmental changes, though as proteins go they do appear to be designed for quick deactivation (i.e. PTH has three regions of the peptide that may have some effect - its actions remain imperfectly known, as of the mid 1990's when I studied it - and they are strung out along a peptide chain such that almost any cleavage will seperate one from the other two.)

The other big class is the steroid hormones, a large group of homeostasis and sex hormones, like testosterone, the oestrogens (there are three types), cortisol and aldosterone. They are all made in the adrenal gland from a cascade of enzyme mediated reactions that start with cholesterol as their raw material (though the total usage requirement of cholesterol by the adrenal glands is very small compared to even a dieters intake). The half life of steroid hormones in the blood is only enough for them to make a few circuits of the body and the levels of these chemicals in the blood is carefully maintained and tweaked from minute to minute.

In the adrenal medulla, the catecholamines are made. They are broadly chemically similar to steroids but have a half life of minutes or seconds. These are adrenaline and epinepherine which can flood into the bloodstream and deliver their simple message - "Fight of Flee!" in seconds. They represent high technology of the chemical communications net.

There are a bunch of other chemicals that have been used to signal remote areas. Thyroxine has a different approach to its production, activation and feedback. Several hormones trigger other (usually peptide) hormones in their target tissue whose only function, apparently, is to act as feedback for the remote secreting gland.

And hormones are still being discovered: I was studying PTH-related peptide [PTHrp] 10 years ago. It had been found about a decade previously and, as you can tell by the name, no-one was even sure if it had a function (though it certainly acted a bit like a slow-moving, long lasting PTH - the best guess back then was that smoothed out the calcium metabolism due to its longevity thus counteracting other, overzealous hormones especially at puberty and old age). Atrial Natriuretic Factor [ANF] - or various other acronyms - was accepted as real more recently (or is it accepted still? I am 10 years out of date). It was like the 'fifth force' in physics, often suggested as an explanation of an oddity but without evidence. It turns out that it is very short lived and volatile and hard to capture in the laboratory. Its effect may be only to perform very short term tweaks of the bodys water balance to even out blood pressure - hard to spot clinically.

 

Before I sign off I want to mention the complement system. Its arguable whether they should be called hormones as their site of production is not fixed and their range is tiny but on the scale of 1mm of blood vessel instead of the body entire the similarities are there. The complement system will cascade through 20 or so levels of one molecule type stimulating secretion of the next type in just a few seconds per level creating a fountain of chemical gradients that is information intensive, telling the distance from and time since the initiating insult occurred to every object in range(in the same way that an osteoarcheologist can learn the original homeland of a creature from the composition of isotopes in a sample compared with those known to exist at all locations). That is a fine-tuned, highly specialised system of chemical processes whose rates of production and decomposition is a vital part of its workings.

[Mokele]

Very interesting stuff, thanks! However, I have a less technical, more historical question:

 

'Hormone' is one of those terms, like 'vitamin' that was brought into being before the science was mature

 

I know that 'vitamin' comes from 'vital amine', because they thought, early on, that all vitamins were amines, but what's the etymology of 'hormone'?

 

Mokele

[Skye]

From the Greek for make stuff happen.

[gene]

thanks Xavier.

 

So, from what i can understand, different hormones have different life-spans?

 

"Before I sign off I want to mention the complement system. "

Regarding this complement system, do you mean there are similar-like substances like hormones that play a part? Like co-enzyme and enzyme?

[mak10]

I know that 'vitamin' comes from 'vital amine', because they thought, early on, that all vitamins were amines, but what's the etymology of 'hormone'?

 

According to Merriam-Webster, its derived from the Greek word hormOn, present participle of horman to stir up, from hormE impulse, assault; akin to Greek ornynai to rouse.

 

-mak10

[mak10]

I know that 'vitamin' comes from 'vital amine', because they thought, early on, that all vitamins were amines, but what's the etymology of 'hormone'?

 

According to Merriam-Webster, its derived from the Greek word hormOn, present participle of horman to stir up, from hormE impulse, assault; akin to Greek ornynai to rouse.

 

-mak10