HARMONES types of harmones classifications

1. Hormones
Hormones are chemical messengers that are secreted directly into the blood, which carries them
to organs and tissues of the body to exert their functions. There are many types of hormones that
act on different aspects of bodily functions and processes. Some of these include:
 Development and growth
 Metabolism of food items
 Sexual function and reproductive growth and health
 Cognitive function and mood
 Maintenance of body temperature and thirst
Where are they secreted from?
Hormones are secreted from the endocrine glands in the body. The glands are ductless, so
hormones are secreted directly into the blood stream rather than by way of ducts. Some of the
major endocrine glands in the body include:
 Pituitary gland
 Pineal gland
 Thymus
 Thyroid
 Adrenal glands
 Pancreas
 Testes
 Ovaries
These organs secrete hormone in microscopic amounts and it takes only very small amounts to
bring about major changes in the body. Even a very slight excess of hormone secretion can lead
to disease states, as can the slightest deficiency in a hormone
Hormonal signaling involves the following steps:
1. Biosynthesis of a particular hormone in a particular tissue
2. Storage and secretion of the hormone
3. Transport of the hormone to the target cell(s)
4. Recognition of the hormone by an associated cell membrane or intracellular
receptor protein
5. Relay and amplification of the received hormonal signal via a signal
transduction process: This then leads to a cellular response. The reaction of the target
cells may then be recognized by the original hormone-producing cells, leading to

2. a down-regulation in hormone production. This is an example of a homeostatic negative
feedback loop.
6. Breakdown of the hormone.
Hormone Classification:
Steroid hormones help control metabolism, inflammation, immune functions, salt and
water balance, development of sexual characteristics, and the ability to withstand illness and
injury. The term steroid describes both hormones produced by the body and artificially produced
medications that duplicate the action for the naturally occurring steroids
Peptide hormones
The structure of peptide hormones is that of a polypeptide chain (chain of amino acids). The
peptide hormones include molecules that are short polypeptide chains, such as antidiuretic
hormone and oxytocin produced in the brain and released into the blood in the posterior pituitary
gland. This class also includes small proteins, such as growth hormones produced by the
pituitary, and large glycoprotein, such as follicle-stimulating hormone produced by the pituitary .
Secreted peptides, such as insulin, are stored within vesicles in the cells which synthesize them.
They are then released in response to stimuli (e.g., as high blood glucose levels in the case of
insulin). Amino acid-derived and polypeptide hormones are water-soluble and insoluble in lipids.
These hormones cannot pass through plasma membranes of cells; therefore, their receptors are
found on the surface of the target cells.
Amino Acid-Derived Hormones
The amino acid-derived hormones are relatively small molecules derived from the amino acids
tyrosine and tryptophan. Examples of amino acid-derived hormones include epinephrine and
norepinephrine, which are synthesized in the medulla of the adrenal glands, and thyroxine, which

3. is produced by the thyroid gland. The pineal gland in the brain makes and secretes melatonin,
which regulates sleep cycles.