Physiology of The Adrenals

The Adrenal Glands

The two adrenal glands (also called the suprarenal glands) are situated in the abdomen, above the kidneys.

Each gland consists of an:

  1. Outer cortex – yellow in color
  2. Inner medulla – dark red or grey in color grey.

The cortex consists of three distinct zones:

  1. Zona Glomerulosa
  2. Zona Fasciculata
  3. Zona Reticularis

Each zone secretes different types of hormones:

  1. Zona Glomerulosa secretes mineralocorticoid (aldosterone)
  2. Zona Fasciculata secretes glucocorticoid (cortisol)
  3. Zona Reticularis secretes sex hormones (progesterone, estrogen precursors and androgens)

Aldosterone

  1. Secreted from the Zona Glomerulosa
  2. Functions of aldosterone include:
  3. Increases sodium retention throughout the body
  4. Increases potassium excretion
  5. Increases water retention
  6. Increases extracellular volume
  7. Enhances the activity of the sodium/potassium pump
  8. Helps “bring on line” the sodium and potassium channels in the luminal membrane in the kidneys

Glucocorticoid (Cortisol)

  1. Secreted from the Zona Fasciculata
  2. Functions of Glucocorticoid (Cortisol) Include:
    1. Mobilizes and increases amino acids in blood and liver by promoting protein catabolism
    2. Stimulates liver to convert amino acids to glucose
    3. Stimulates increased glycogen in the liver
    4. Inhibits glucose utilization in the peripheral tissue
    5. Mobilizes and increases fatty acids in the blood by supporting synthesis of hormone sensitive lipase
    6. Counters inflammation and allergies
    7. Prevents loss of sodium in urine and helps maintain blood volume and blood pressure
    8. Sustains tissue responsiveness to catecholamines
    9. Maintains resistance to stress
    10. Maintains personality and emotional stability
    11. Modulates thyroid function

Sex Hormones (DHEA)

  1. Secreted by the Zona Reticularis
  2. Functions of DHEA include:
  3. Acting as an androgen with anabolic activity
  4. Precursor to testosterone
  5. Precursor to estrogen and progesterone
  6. Reverses immune suppression caused by excessive cortisol level and therefore improves resistance to viruses, bacteria, candida albicans, parasites, allergies and cancer
  7. Functions of DHEA include:
    1. Stimulates bone deposition and remodeling, which can help prevent osteoporosis6.Improves cardiovascular status by lowering total and LDL cholesterol levels, lessens incidence of heart attack
    2. Increases muscle mass
    3. Decreases percentage body fat
    4. Reverses many of the unfavorable effects of excess cortisol and help create an improvement in: energy, vitality, sleep, PMS, and mental clarity
    5. Can help with quicker recovery from any kind of acute stress: insufficient sleep, excessive exercise, mental strain etc.

The Adrenal Medulla

  1. Contains chromaffin cells (also called phaeochromocytes)
  2. These cells are surrounded by a meshwork of blood vessels called venous sinusoids.
  3. The chromaffin cells, when stimulated by the sympathetic nervous system secrete noradrenaline and adrenaline into the sinusoids, which are delivered by the bloodstream to the rest of the body.