03 Adrenal Steroids Flashcards
Are steroids stored for later use?
No, they are synthesized when needed
Rate of secretion = rate of synthesis
Where is aldosterone synthesized?
Zone glomerulosa
Synthesized from cholesterol
Where is cortisol synthesized?
Zona fasciculata and reticularis
Synthesized from cholesterol
What controls the synthesis of cortisol?
Adrenocorticotropic Hormone (ACTH)
What controls the synthesis of aldosterone?
Angiotensin II and plasma K+
Are steroids free in plasma?
No, 90% bound in plasma to corticosteroid binding globulin (CBG) and Albumin
How are steroids inactivated?
Steroids are inactivated in the liver by making it more polar for urine excretion
- Reduction of A ring
- Sulfate conjugation
- Glucuronide conjugation
How does a corticosteroid produce an effect?
- Binds to cytosolic steroid receptor
- Translocated to nucleus
- Stimulates transcription of mRNA
- Stimulates mRNA directed protein synthesis
- Proteins mediate glucocorticoid effect
What mediates carbohydrate and protein metabolism?
Mediated by glucocorticoid receptor
Enhances liver gluconeogenesis from protein and stimulates AA mobilization from muscle, skin, etc.
- Increased plasma glucose and liver glycogen
- Increased urinary Nitrogen excretion
- Reduces peripheral glucose utilization
How is lipid metabolized?
There is a redistribution of body fat
Stimulates release of fatty acids from adipose tissue
How are minerals and electrolytes metabolized?
Mediated by mineralocorticoid receptor in kidney bound by cortisol and aldosterone
- Increased Na+ reabsorption
- Increased K+ and H+ excretion
- Hypertension
What is the effect of corticosteroids on the immune system’s ability to traffic cells?
Reduced access of cells to target tissue
- Lymphocytopenia and monocytopenia –redistribution of cells out of vascular space
- Prevent neutrophil adherence to endothelium
- Inhibit action of chemotactic factors
What is the effect of corticosteroids on macrophages and lymphocytes?
Macrophage:
- inhibit Ag processing
- inhibit binding to Fc receptor
- inhibit synthesis and release of IL-1
T-lymphocytes:
- interfere with macrophage Ag processing
- interfere with lymphokine action
- absence of IL-1 prevents activation
- reduces IL-2 synthesis
What is the anti-inflammatory activity of corticosteroids?
a. Inhibits signs and symptoms of inflammation by inhibiting immune system.
b. Inhibits arachidonic acid release so synthesis of prostaglandins and leukotrienes is reduced.
c. Inhibits induction of cyclooxygenase-2 by cytokines.
d. Decrease capillary permeability
In most cases is steroid use curative?
Use is not etiological or curative in most cases. Palliative or symptomatic therapy.
Why shouldn’t you abruptly discontinue corticosteroid therapy?
With prolonged use of steroids, the adrenal gland atrophies. If abruptly discontinue steroid therapy, will result in acute adrenal insufficiency of both mineralocorticoid and glucocorticoid steroids.
No mineralocorticoid activity = increased excretion of Na+ and H2O and decreased K+ excretion = hypertension and hyperkalemia.
