Page 114 - Clinical Biochemistry

Chapter 11:

Hormones

Outlines

• Types of hormones
• The major glands of the endocrine system and hormones secreted from them
• Disease associated with the major glands of the endocrine system

A hormone: is a chemical substance released by a cell or a gland in one part of the body that
sends out messages that affect cells in other parts of the organism.
Types:
1. Amine-derived hormones: are derivatives of the amino acids tyrosine and tryptophan.
Examples: catecholamines and thyroxine.
2. Peptide hormones: consist of short chains of amino acids.
Examples: Vasopressin and thyrotropin releasing hormone (TRH).
3. Proteins: peptides composed of scores or hundreds of amino acids.
Examples: insulin and growth hormone.
4. More complex protein hormones: carry carbohydrate side chains and are called
glycoprotein hormones.
Examples: Luteinizing hormone (LH), Follicle-stimulating hormone (FSH), Thyroid-
stimulating hormone (TSH).
5. Lipid and phospholipid hormones: are derived from lipids such as linoleic acid and
phospholipids such as arachidonic acid. The main class is the eicosanoids, which includes the
widely studied prostaglandins.
6. Steroid hormones: are derived from cholesterol. The adrenal cortex and the gonads are
primary sources. Examples: testosterone and cortisol.
The Endocrine System
The major glands of the endocrine system are the hypothalamus, pituitary, thyroid,
parathyroids, adrenals, pineal body, and the reproductive organs (ovaries and testes).