Endo (pt 5/7) Adrenal Flashcards
Describe the cascade of events from Hypothalamus to the release of hormones from the Adrenal Cortex.
1) Stress causes the release of Corticotropin Releasing Factor (CTRF) from the Hypothalamus
2) CTRF communicates with the Anterior Pituitary to release Corticotropin (ACTH)
3) ACTH stimulates the Adrenal Cortex to release gluco or mineralocorticoids.
Have important effects on:
-Intermediary metabolism (the intracellular process by which nutritive material is converted into cellular components)
-CV function
-Growth
-Immune Function
Glucocorticoids (Cortisol)
Controlled primarily by circulating Angiotensin and Potassium.
-Important salt-retaining effects
Mineralocorticoids (Aldosterone)
A normal adult, in the absence of stress, secretes 10-20 mg/day.
-Secretion follows circadian rhythm (highest in AM and after meals, declining throughout the day)
-Governed by pulses of ACTH
Cortisol
What time of day is best to administer exogenous cortisol?
Evening, because patients are most sensitive to PM dosing of exogenous steroids due to the decline of endogenous steroids in the evening.
90% of endogenous Cortisol is bound to ____ in the plasma, and 5% is bound to ____, leaving 5% free.
CBG; Albumin
Endogenous cortisol doesn’t rly bind to Albumin, but synthetics do, like _____.
Dexamethasone (synthetics bind to albumin, not CBG)
What is the half-life of Cortisol, and what makes it increase/decrease?
1/2 = 60-90 min
Increase: exogenous administration, stress (Surgery)
Decrease: hypothyroidism, liver dz
How is Cortisol metabolized and excreted?
Hepatic metabolism, urinary excretion.
1% excreted unchanged
20% converted to Cortisone
30% excreted as dihydroxy ketone metabolites
Explain the pharmacodynamics of Cortisol
1) Cortisol is present in the blood bound to Corticosteroid Binding Globulin (CBG).
2) Cortisol is added to the receptor, making it unstable.
3) Cortisol can now cross into the nucleus of the cell, where it binds with Nuclear Receptors (GRE), regulating transcription of the target gene.
___ - ____% of all genes are regulated by glucocorticoids.
10-20%.
Significant amount of actions r/t growth factors that are produced from the combination of steroid + receptor that moved into transcription. After gene transcription occurs, we see the anti-inflammatory, anti-growth, and immunosuppressive effects of glucocorticoids.
What are some of the physiologic effects of Cortisol?
-Cortisol can stimulate Mineralocorticoid receptors as well.
-Provides negative feedback to the Anterior Pituitary to suppress ACTH release
-Influence the function of most cells of the body
-Necessary for the vascular and bronchial smooth muscle responses to catechols
-Necessary for the for the lypolytic response of fat cells to catechols, ACTH and GH
What are the effects of mineralocorticoid receptor stimulation by cortisol?
-Sodium and fluid retention with a loss of Potassium (Hypokalemia, hypochloremic alkalosis, HTN)
-IF pt has low protein, renal disease or liver disease they will show signs of fluid overload and edema
-IF pt has heart disease, Sodium retention will promote heart failure
-Pts may need: Potassium supplements, Sodium/Salt restrictions, No additional mineralocorticoid therapy
What are the effects of Cortisol mainly due to?
Proteins synthesized from mRNA transcribed from their target organs
Where are the catabolic/anti-anabolic effects of Cortisol seen?
Seen mostly in Lymphoid, connective tissue, muscle, peripheral fat and skin
What are the catabolic & anti-anabolic effects of Supraphysiologic amounts (high doses) of glucocorticoids?
↓Muscle mass
Thinning of skin
Anti-anabolic effect on bone (Ex. osteoporosis of Cushing’s Syndrome)
What are the anti-inflammatory effects of glucocorticoids?
-Profound effects on the concentration, distribution, & function of peripheral leukocytes
-Suppressive effects on the inflammatory cytokines, chemokines & other inflammatory mediators
What are the Immunosuppressive effects of a Single dose of short-acting glucocorticoid?
-Inc Neutrophil concentration
-↓ Lymphocytes, monocytes, eosinophils & basophils
-Peak effect = 6hrs and then decrease starting at 24hrs
What are the Immunosuppressive effects of a Large dose (20mg/d prednisone) of glucocorticoid?
Decreased Antibody production, leading to:
-↓ ability to phagocytose and kill micro-organisms
-↓ TNF alpha, interleukin, metalloproteins, plasminogen factor (dec signaling of immune system)
General Immunosuppressive effects of Glucocorticoids?
-Inhibit phospholipase A2
-↓COX2 and therefore ↓ prostaglandins
-Transdermal: Vasoconstriction (suppression of mast cell degranulation, decreased histamine release from mast cells and basophils)
What are some misc. results of increased glucocorticoids?
-Insomnia, euphoria, depression and ↑ ICP (pseudotumor cerebri)
-Suppression of ACTH, GH, TSH, & LH
-Peptic Ulcer Disease
-Fat redistribution to viscera, face, nape of neck and supraclavicular
-Antagonize the effects of Vit D on Calcium absorption
-↑ RBC’s and platelets
Glucocorticoids have a dose related effect on ______, _______, and _____ metabolism.
carbohydrates, proteins, and fat
What is the metabolic goal of glucocorticoids?
Goal: maintain adequate glucose supply to the brain. Brain will steal glucose from everything else (pull up from proteins and fats).
How will glucocorticoids sacrifice muscle to make glucose available for the brain?
1) Stimulate phosphoenol carboykinase, G6phosphatase, glycogen synthesis, and the release of AAs in the course of muscle catabolism
2) Inhibit the uptake of glucose by muscle cells.
Increased insulin release stimulates what related to fats?
Increased insulin release (from increased serum glucose) stimulates lipogenesis and inhibits lipolysis = net increase in fat deposition + increased release of fatty acids and glycerol
What do glucocorticoids do in a fasting state to contribute to the glucose supply in the brain?
-Glucose from gluconeogenesis
-Release of amino acids from muscle catabolism
-Inhibition of peripheral glucose uptake
-Stimulation of lipolysis
Cortisol Deficiency can have what systemic effects?
-Impair renal function
-Increased vasopressin secretion
-Decreased ability to excrete H20
-Fetal Lung immaturity
Explain why infants need glucocortoids if mom is cortisol deficient?
-Glucocorticoids stimulate surfactant development in the fetus.
-Betamethasone 12mg IM x 1 dose with an additional dose 18 – 24h later
-Reduces the incidence of respiratory distress syndrome in premature infants (earlier than 34 weeks).