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Adrenal Cortex Hormones

Notes

Adrenal Cortex Hormones

Sections



The adrenal glands sit on top of the kidneys; they comprise an inner medulla and an outer cortex

Position in the Body:

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Histology Overview:

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Medulla

The medulla accounts for approximately 20% of the total adrenal tissue.

It Is of neuroectodermal origin.

Secretes the catecholamines:
Epinephrine
Norepinephrine

Cortex

The cortex accounts for the other 80% of the adrenal gland.

It is of mesodermal origin.

Secretes:
Mineralocorticoids.
Glucocorticoids.
Androgens.

Adrenal Cortex Hormones

Hormonal secretion is triggered by ACTH stimulation (from anterior lobe of pituitary),

In response to ACTH, it secretes steroid hormones; cholesterol is common precursor.

Enzyme availability accounts for differential hormonal production in the cortical layers.

Zona reticularis

Primarily produces androgens, including DHEA and androstenendione, which are precursor hormones that can be converted to testosterone and estradiol; thus, they are a non-gonadal source of "sex-steroids."

Zona fasciculata

Primarily produces glucocorticoids, including cortisol, which has multiple effects throughout the body:
Increases gluconeogenesis and glycogen storage
Suppresses the inflammatory response
Maintains vascular response to catecholamines.

Thus, it is secreted in response to mental or physical stressors.

Zona glomerulosa

Produces mineralocorticoids

Specifically, angiotensin II (which we discuss in renal physiology), drives the production of aldosterone, which increases sodium reabsorption and potassium secretion in the late distal tubules and collecting ducts of the nephron.

Thus, it is secreted in response to decreased extracellular fluid volume to conserve body water.

Clinical Correlations

Adrenal cortex malfunction has deleterious effects; these effects are predictable based on the source of the deficiency.

Primary adrenocortical insufficiency, aka, Addison's disease

The destruction of the adrenal cortex inhibits hormone production.

A distinguishing characteristic of this disorder is that ACTH levels are high, which causes hyperpigmentation. In healthy individuals, circulating cortical hormones inhibit secretion of ACTH from the anterior pituitary via negative feedback; in the absence of cortical hormone production, ACTH secretion goes unchecked.

Secondary adrenocortical insufficiency

ACTH secretion is insufficient to stimulate conversion of cholesterol for production of the cortical hormones.

Incidentally, aldosterone levels may be normal, because its production does not depend on increased levels of ACTH.

Cushing's Syndrome

Refers to collection of signs and symptoms caused by excess cortisol production:
Hypertension, hyperglycemia, muscle wasting, "moon face," and central obesity (fat deposits disproportionally at the core).

Excessive cortisol production can be caused by a variety of factors, including glucocorticoid drugs or pituitary tumors (Cushing's disease).

Drugs that reduce cortisol secretion can be used to counteract some of these effects.

Full-Length Text

  • Here we will learn about the hormonal products of the adrenal gland, with a special focus on the adrenal cortex.
  • To begin, start a table.
  • Denote that the adrenal gland comprises a medulla and a cortex.
  • Denote that the medulla:
    • Comprises the inner region of the gland.
    • Accounts for approximately 20% of the total adrenal tissue.
    • Is neuroectodermal origin, and in response to neural stimulation --
    • Secretes the catecholamines:
      Epinephrine
      Norepinephrine.
  • Denote that the adrenal cortex, which will be the focus of our tutorial:
    • Comprises the outer region.
    • Accounts for the other 80% of the adrenal gland.
    • It is of mesodermal origin.
    • Responds to ACTH from the anterior pituitary, and in response
    • Secretes each of the three subclasses of steroid hormones:
      Mineralocorticoids.
      Glucocorticoids.
      Androgens.

Let's illustrate the adrenal gland and the locations of hormone production.

  • First, draw the medulla, which is the innermost region.
  • Indicate that it secretes the catecholamines.

Next, show the three cortical layers:

  • From deep to superficial, the:
    • Zona reticularis, which primarily produces androgens,
    • Zona fasciculata, which primarily produces glucocorticoids, and, the
    • Zona glomerulosa, which produces mineralocorticoids.

Let's take a closer look the synthesis and actions of these hormones;

  • First, draw a schematic of the adrenal cortex and its three layers, the zona glomerulosa, zona fasciculata, and zona reticularis.
  • Then, show that ACTH (adrenocorticotropic hormone), which is synthesized and released by the anterior lobe of the pituitary gland, stimulates the adrenal cortex to convert cholesterol:
  • In the zona glomerulosa, cholesterol is converted to mineralocorticoids;
  • Specifically, indicate that angiotensin II (which we discuss in renal physiology), drives the production of aldosterone.
    • Aldosterone increases sodium reabsorption and potassium secretion in the late distal tubules and collecting ducts of the nephron;
    • Thus, it is secreted in response to decreased extracellular fluid volume to conserve body water.
  • Next, indicate that the zona fasciculata produces the glucocorticoids;
    • For example, write that cortisol, which has multiple effects throughout the body, increases gluconeogenesis and glycogen storage, suppresses the inflammatory response, and maintains vascular response to catecholamines.
    • Thus, it is secreted in response to mental or physical stressors.
    • The zona reticularis produces androgens, including DHEA and androstenendione;
    • These are precursor hormones that can be converted to testosterone and estradiol; thus, they are a non-gonadal source of "sex-steroids."

Given that the adrenal cortex produces a variety of hormones with widespread effects, adrenal cortex malfunction has deleterious effects; these effects are predictable based on the source of the deficiency.

  • Write that, in primary adrenocortical insufficiency, aka, Addison's disease, the destruction of the adrenal cortex inhibits hormone production.
    • A distinguishing characteristic of this disorder is that ACTH levels are high, which causes hyperpigmentation.
    • In healthy individuals, circulating cortical hormones inhibit secretion of ACTH from the anterior pituitary via negative feedback; in the absence of cortical hormone production, ACTH secretion goes unchecked.
    • Conversely, in secondary adrenocortical insufficiency, ACTH secretion is insufficient to stimulate conversion of cholesterol for production of the cortical hormones.
    • Incidentally, aldosterone levels may be normal, because its production does not depend on increased levels of ACTH.
  • Finally, write that Cushing's Syndrome refers to collection of signs and symptoms caused by excess cortisol production:
    • Hypertension, hyperglycemia, muscle wasting, "moon face," and central obesity (fat deposits disproportionally at the core); these effects are predictable, given cortisol's physiological actions.
    • Excessive cortisol production can be caused by a variety of factors, including glucocorticoid drugs or pituitary tumors (Cushing's disease).
    • Drugs that reduce cortisol secretion can be used to counteract some of these effects.