Adrenal Gland Hormones Overview

Adrenal Gland Organization and Hormone Production

• The adrenal gland is made up of 3 layers:
  • Zona Glomerulosa
  • Zona Fasciculata
  • Zona Reticularis
• Each layer produces different types of hormones.
  • The Zona Glomerulosa produces Mineralocorticoids such as Aldosterone.
  • The Zona Fasciculata produces Glucocorticoids such as Cortisol and Corticosterone.
  • The Zona Reticularis produces Androgens such as Dehydroepiandrosterone.
• The Adrenal Medulla produces stress hormones such as Epinephrine and Norepinephrine.

Functions of Adrenal Hormones

• Mineralocorticoids regulate mineral balance, with Aldosterone specifically acting on the kidneys to increase Na+ reabsorption.
• Glucocorticoids regulate glucose metabolism. Cortisol and Corticosterone act on various targets, including muscles, adipose tissue, immune cells and the liver.
• Androgens regulate testosterone levels. Dehydroepiandrosterone specifically stimulates armpit hair growth.
• Stress hormones, such as Epinephrine and Norepinephrine, stimulate the sympathetic nervous system.

Regulation of Cortisol

• Cortisol regulation is a feedback loop involving the hypothalamus, anterior pituitary, and adrenal cortex.
• The hypothalamus produces Corticotropic Releasing Hormone (CRH) which stimulates the anterior pituitary to produce Adrenocorticotropic Hormone (ACTH).
• ACTH then stimulates the adrenal cortex, specifically the Zona Fasciculata, to produce cortisol.
• Cortisol then acts on the hypothalamus and anterior pituitary to decrease the production of CRH and ACTH, thus completing the feedback loop.

Effects Of Cortisol

• Cortisol has widespread actions on the body, including:
  • Muscle: Cortisol increases protein catabolism, breaking down proteins into amino acids.
  • Adipose Tissue: Cortisol enhances lipolysis, breaking down triglycerides into glycerol and fatty acids.
  • Liver: Cortisol promotes gluconeogenesis, the production of glucose from non-carbohydrate substrates like amino acids and glycerol.
  • Immune System: Cortisol suppresses immune function, making the body more susceptible to infections.

Cushing's Disease – Cortisol Hypersecretion

• Cushing's disease is caused by the overproduction of cortisol, leading to various symptoms including:
  • Hyperglycemia: High blood glucose levels due to increased gluconeogenesis.
  • Muscle Wasting: Muscle atrophy and weakness due to increased protein catabolism.
  • Thinning Skin: Thinning of the skin with tearing due to protein degradation.
  • Stunting Growth: Reduced growth and osteoporosis due to the breakdown of bone tissue.
  • Increased Infections: Increased susceptibility to infections due to suppressed immune function.
  • Adipose Redistribution: Fat accumulation in specific regions of the body.

Glucocorticoids

• Glucocorticoids are synthetically produced drugs that mimic the effects of Cortisol.
• They are used to suppress inflammation and allergic reactions.
• They are also used to treat autoimmune diseases like rheumatoid arthritis and to prevent transplant rejection.
• Glucocorticoids are used as pain relief, often in cortisone injections for joint pain.
• Glucocorticoids can also be used as replacement therapy in cases of adrenal insufficiency.

Side effects of Glucocorticoids

• They can cause various side effects:
  • Increased Appetite: Leading to weight gain.
  • Acne
  • Thinned Skin: Thinning of the skin, making it prone to bruising.
  • Increased Risk of Infections: Suppressed immune function makes the body more susceptible to infections.
  • Mood Changes: Mood swings and depression are common side effects.
  • Diabetes: Increased risk of developing diabetes due to their effect on blood glucose levels.
  • High blood pressure.
  • Osteoporosis: Thinning bones, making them brittle and prone to fractures.
  • Withdrawal Symptoms: Sudden cessation of glucocorticoid use can lead to adrenal gland suppression.

The Adrenal Medulla

• The Adrenal Medulla produces stress hormones, most notably Epinephrine.
• Epinephrine is a catecholamine, a hydrophilic amine that stimulates the fight-or-flight response of the sympathetic nervous system.
• Epinephrine triggers various effects in the body, including:
  • Increased Gluconeogenesis.
  • Increased Heart Rate: To deliver more oxygen and nutrients to muscles.
  • Relaxed Lung Airways: To improve oxygen intake.
  • Increased Blood Pressure: By constricting blood vessels, redirecting blood flow to vital organs.