Official definition of a hormone?

[seacucumber]

Can someone please provide me with a fool-proof definition I can always use??
I obviously know what hormones are but all definitions I have seen seem to not cover everything, eg. they always say hormones "travel throughout the whole body" but that doesn't happen with autocrine and paracrine systems...

[AbominableMowman]

Hormones are organic molecules (chemicals) produced and secreted by one type of cell (e.g. an endocrine gland cell) that travel via extracellular fluid (often blood), act on specific target cells and are effective in minute amounts.

[Scooby]

Hormones are organic molecules (chemicals) produced and secreted by one type of cell (e.g. an endocrine gland cell) that travel via extracellular fluid (often blood), act on specific target cells and are effective in minute amounts.

Careful. Hormones aren't necessary secreted by glands, nor do they necessarily travel to a specific target cell via an extracellular fluid, nor are they always effective in small amounts

Individual cells can secrete and then respond to their own hormones (ie. autocrine signalling). A T cell produces IL2 during an immune response, which then binds back onto that cell and triggers it to proliferate. Patients with type II diabetes are essentially insulin resistant - even though insulin is present in ample amounts, their cells don't respond to it effectively

You can only really give a general definition for a hormone, since there's so many of them, and many have different properties. You can really only say that "a hormone is a chemical messenger released by a cell or group of cells that acts on a specific receptor to trigger a response" without being inaccurate

[Yacoubb]

Hormones are chemical signalling molecules produced by a cell, that can act upon cells they are produced by or transported short or long distances to specific target cells they act upon, enabling communication to occur within living organisms.

Is that okay?

[Scooby]

Hormones are chemical signalling molecules produced by a cell, that can act upon cells they are produced by or transported short or long distances to specific target cells they act upon, enabling communication to occur within living organisms.

Is that okay?

Yup