The Endocrine System

1) The endocrine system uses hormones (chemical signals) to send messages through the blood stream to distant cells in the body.

2) Hormones control a wide range of activities in the cell including metabolism, growth and reproduction.

3) Based on chemical structure, there are 3 types of hormones:

  • peptide hormones - made from amino acids
  • steroids - made from cholesterol
  • prostaglandins - made from lipids
  • 4) The human body produces at least 50 different hormones- some examples are shown below, along with the location of their production.

    Examples of Hormones and the Location of Production

    5) Hormones are produced by many different organs in the body including the hypothalamus, pineal gland, pituitary gland, adrenal glands, thymus gland, thyroid gland, parathyroid gland, pancreas, testes and ovaries. Secondary endocrine organs also are involved in the production and regulation of some hormones.

    Location of Endocrine Organs

    6) You'll notice in the above figure that several of these endocrine glands are located in the brain. Below is a closeup of their location.

    Pineal Gland Figure

    7) The hypothalamus produces the hormones oxytocin and antidiuretic hormone (ADH). Oxytocin helps regulate contractions of the uterus during labor as well production of milk for breastfeeding. ADH (also known as vasopressin regulates urine production by the kidneys.

    The Pituitary Gland

    8) The pituitary gland produces a number of important hormones including growth hormone (GH), prolactin (PRL), thyroid-stimulating hormone (TH), adenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH) and luteinizing hormone (LH).

    Hormone Action

    9) The thyroid gland produces the hormones thyroid hormone and calcitonin.

    10) The parthyroid glands produce parthyroid hormone.

    11) The adrenal glands are located above the kidneys. They produce several important hormones including androgens, estrogens, cortisone and cortisol.

    Adrenal Glands Figure

    12) The pineal gland produces the hormone melatonin.