HORMON

Nove HidajatiFaculty of Veterinary Medicine Airlangga UniversitySurabaya

What is hormon?

Many organs in the body secreted biologically active compound called endocrine hormones, which are transported via blood stream to other tissues or organs where they exert a biological effect

As classically defined, is a substance that is synthesized in one organ and transported by the circulatory system to act on another tissue

Hormones can act on adjacent cells (paracrine)

Hormones can act on the cell in which they were synthesized without entering the sistemic circulation (autocrine)

What is the importance of hormones?

Several hormones may control one, process or one hormon may control several process

Provide communication beetween cells, tissues and organs

This comunication is responsible for the regulation of wide range of functions including growth, reproduction, development, homeostasis, and response to external stimuli. Failure in this comunication channels are common and lead to many diseases of the endocrine system

How do hormones act?

In order to act , hormones must interact with other loci on or in the target cell

These sites are termed receptors

A receptor is a locus to which the hormone binds in order to elicit its action

RECEPTOR

A receptor has two function :First, it must be able to distinguish the

hormone from all the other chemicals present in the circulation and bind it.

The hormone binding sites on receptors have evolved to have unique configurations that are complementary to the hormones they bind.

Generally, hormone-receptor interactions are noncovalent in nature and are reversible.

RECEPTOR

- Second, the receptor must able to transmit the information gained from the binding to trigger a cellular response.

Thus, subtances that bind hormones, even tightly, but do not trigger subsequent responses are not receptors.

Types of Hormones

Hormon can be clasisified in several ways, according:

1-Chemical composition : Cholesterol derivates– this

include : glucorticoid, mineralocorticoid, esterogen, progestin Amino acid -tyrosine Polypeptyde-ACTH,TRH Glycoprotein-TSH, FSH, LH

2-Solubility properties-lipophilic dan hidrophilic3-Location of reseptor 4-Nature of signaling used to mediate hormonal

action within the cell

Clasification of hormones by mechanism of action

Group I hormones Hormon that bind to intracellular

receptors Androgens calcitriol esterogens glucocorticoids mineralocorticoids progestins retinoic acid

Group II HormonesHormones that bind to cell surface

receptors

A.The second messenger is cAMPCalcitonin, glucagon, LH, Somatosatin,

B.The second mesenger is cGMPNitric oxide, atrial natriuretic factor

C.The second messenger is calcium or phosphatidyl inositols (or both)

Gastrin, oxitocyn, cholecistokinin, TRH, Acetilcholin

D.The second messenger is a kinase or phosphatase cascadeAdponectin, insulin , leptin, GH, Prolactin, IGF-I , IGF-II, EGF

General features of hormon classes

Group I Group II

Types Steroid, iodothyronines,calcitriol, retinoids

Polypeptides, protein, glycoproteins, cathecolamines

Solubility Lipophilic Hydrophilic

Transport protein Yes No

Plasma halflife Long ( hours to days) Short (minutes)

Receptor Intracellular Plasma membran

Mediator Receptor-hormone complex

cAMP.cGMP, Ca2+,metabolites complex phosphoinositols, kinase cascade

WHERE HORMONES ARE SYNTHESIZED?

Hormones are synthesized in discrete organs designed solely for spesific purpose

Pituitary: TSH, FSH, LH, GH, Prolactin, ACTH

Some organs are disigned to perform two distinct but closely related function

Ovaries produce mature oocyte and reproductive hormones estradiol and progesteron

The testes produce mature spermatozoa and testesterone

Hormones are also produced in specialized cells within other organs

Small intestine : glucagon like peptide Thyroid : calcitonin Kydney : angiotensin II

The synthesis of some hormones requires the parenchimal cells of more than one organ

Skin, liver, kidney : calcitriol.

Hormon are synthesized and modified for full activity in a variety of ways

Some hormones are synthesized in final form and secreted immediattely , included in this class are the hormon derived from cholesterol

Others are synthesized in final form and stored in producing cells, example catecholamine

The others hormone synthesized and from precursor molecules in the producing cell, then are processed and secreted upon a physiologic cue, examples insulin

Converted to active forms from precurssor molecules in the periphery, examples: T3, DHT