Lecture 20. Steroid hormones

into three zones that synthesize various steroids from cholesterol and

secrete them.
The outer zona glomerulosa produces mineralocorticoids (for example, Aldosterone) which are responsible for regulated primarily by the renin-angiotensin system.
The middle zona fasciculata synthesizes glucocorticoids (for example, Cortisol) which are concerned with normal metabolism and resistance to stress.
The inner zona reticularis secretes adrenal androgens.

the outer zone, is controlled by pituitary Corticotropin, which is

released in response to the hypothalamic Corticotropin-releasing hormone. Glucocorticoids serve as feedback inhibitors of Corticotropin and Corticotropin-releasing factor secretion.

intracellular cytoplasmic receptors in target tissues.
The receptor-hormone

complex then translocates into the nucleus where it acts as a transcrition factor to turn genes on or off, depending on the tissue.
This mechanism requires time to produce an effect. There are other glucocorticoid effects, such as their requirement for catecholamine – mediated dilation of vascular and bronchial musculature or lipolysis, whose effects are immediate.

– 36 hrs.): Prednizolon
3. Long acting (T1/2>36 hrs): Triamcinolone, Betamethasone

They

can use as therapeutic agents in a variety of disorders.

favor gluconeogenesis by both increasing amino acid uptake by the

liver and kidney and elevating activities of gluconeogenic enzymes.
GCs stimulate protein catabolism (except in the liver) and lipolysis, thereby providing the building blocks and energy needed for glucose synthesis.

By raising plasma glucose levels, GCs provide the body with the energy it requires to combat stress caused, for example, by trauma, fright, infection, bleeding, or debilitating disease.

GCs cause a decrease in eosinophils, basophils, monocytes and lymphocytes. In contrast, they increase the blood levels of hemoglobin, erythrocytes, platelets and polymorphonuclear leukocytes (this property is important in the treatment of leukemia).

therapeutic property of the GCs is their ability to dramatically

reduce the inflammatory response and to suppress immunity.
The exact mechanism is complex and incompletely understood.
However, it is know that the lowering and inhibition of peripheral lymphocytes and macrophages play a role.
Also involved is the indirect inhibition of phospholipase A2 (due to the steroid mediated elevation of lipocortin), which blocks the release of arachidonic acid - the precursor of the prostaglandins and leukotrienes, from membrane-bound phospholipid.

system.
Feedback inhibition of Corticotropin production by

elevated GCs causes inhibition of further glucocorticoid synthesis as well as thyroid stimulating hormone production, whereas growth hormone production is increased.

These are mostly associated with the adverse effects of

the hormones.
High doses of GCs stimulate gastric acid and pepsin production and may exacerbate ulcers.
Effects on the central nervous system that influence mental status have been identified.
Chronic glucocorticoid therapy can cause severe bone loss. Myopathy leads patients to complain of weakness.

disease). This disease is caused by adrenal cortex dysfunction. Hydrocortisone

is given to correct the deficiency.
Replacement therapy for secondary adrenocortical insufficiency. This deficiencies are caused by a defect either in CRF (Corticotropin-releasing factor) production by the hypothalamus or Corticotropin production by the pituitary. Hydrocortisone is also used for these deficiencies.

hypersecretion of GCs that is due to either excessive release

of Corticotropin by the anterior pituitary or to an adrenal tumor. The Dexamethasone suppression test is used to diagnose the cause of an individual’s case of Cushing’s syndrome. This synthetic glucocorticoid suppresses Cortisol release in individuals with pituitary-dependent Cushing’s syndrome, but it does not suppress glucocorticoid release from adrenal tumors.

(for example, rheumatoid and osteoarthritic inflammations, inflammatory conditions of the

skin), including the redness, swelling, heat and tenderness that are commonly present at the inflammatory site.

the symptoms of drug, serum and transfusion allergic reactions, bronchial

asthma and allergic rhinitis. Betamethasone, Triamcinolone, Prednizolone are the most effective.
Autoimmune diseases.
Organ transplantation.
Limphatic leukemia

appetite
hypertension
edema
euphoria
psychoses

increase renal excretion of Ca++ and K+;
decrease renal excretion

of Na+ and water.

as well, orally active, used for:
replacement therapy in Addison’s disease;
congenital

adrenal hyperplasia;
idiopathic postural hypotension.