Adrenal Pharmacology Flashcards
Adrenal Medulla
- Consists mainly of chromaffin cells, which are part of the sympathetic nervous
- Location for the conversion of tyrosine to epinephrine (adrenaline) and norepinephrine (noradrenaline) in response to stress
- Responsible for producing and secreting steroid hormones
Zona glomerulosa
- Predominantly regulated by Angiotensin II and extracellular K+
- Has receptor for ACTH, but ACTH is not the main regulator
- Does NOT undergo atrophy in the absence of ongoing stimulation by ACTH (pituitary gland)
- Renin-angiotensin system regulates aldosterone production and secretion from zona glomerulosa
Aldosterone
- Produced in zona glomerulosa accounts
- Maintains the homeostatic balance of electrolytes, including the renal tubular reabsorption of sodium
- Causes the kidneys to increase sodium and water retention
- Increases blood pressure
- Exerts a negative feedback on renin’s release
Cortisol
- Creates Energy Substrates
- Increases gluconeogenesis
- Proteolysis
- Lipolysis
- Maintains BP
- INCREASING sensitivity of blood vessels to catecholamines (epinephrine and norepinephrine) which narrow blood vessel lumen
- Dampens inflammatory and immune response
- Reduces production of prostaglandins and interleukins
- Inhibits T-lymphocytes
What are the two adrenal androgens?
- Dehydroepiandrosterone (DHEA)
- Dehydroepiandrosterone sulfate (DHEAS)
Adrenal Androgens
- Steroid hormones with weak androgenic activity
- Provide a pool of circulating precursors for peripheral conversion to more potent androgens (e.g. testosterone) and estrogens (e.g. estradiol)
- Adrenarche (secretion of adrenal androgens) occurs BEFORE gonadarche (secretion of gonadal sex steroids). Causes appearance of axillary and pubic hair
What is the transport of cortisol?
- > 90% bound to corticosteroid-binding globulin (CBG)
- Bound steroids are physiologically inactive
- Free cortisol increases when binding sites on CBG become saturated (total plasma cortisol > 20 ug/dL)
What factors enhance glucocorticoids metabolism?
- Phenytoin
- Phenobarbital
- Rifampin
- Mitotane
- Hyperthyroidism
What factors reduce glucocorticoid metabolism?
- Chronic liver disease
- Pregnancy
- Hypothyroidism
- Anorexia nervosa
- Protein-calorie malnutrition
- Estrogens
- Surgery and other major physiologic stresses
What are the glucocorticoid effects?
- Immunologic
- Calcium wasting
- Anti-inflammatory
- Demargination
- Neurologic
What are the mineralocorticoid effects?
- Na+ retention
- K+ secretion
Dexamethasone
- Pure glucocorticoid activity
- Useful for severe inflammation and/or nausea
- Ex: Meningitis or anti-emetic regimen
Methylprednisone
- High glucocorticoid activity
- Useful for immunologic flares
- Ex: Multiple sclerosis, rejection
Hydrocortisone
-Equal action
-Useful for adrenal insufficiency
Ex: Sepsis, Addison’s
Fludrocortisone
- Mineralocorticoid Activity
- Useful for Addison’s disease:
- Treat hyperkalemia and hypotension
Cushing syndrome
Supraphysiologic concentrations of glucocorticoids
What is the etiology of Cushing syndrome?
- Endogenous excess production of cortisol
- ACTH-DEPENDENT
- Pituitary corticotrope adenoma = **Cushing disease **(one form of Cushing Syndrome)
- Ectopic secretion of ACTH by NON-pituitary tumor
- ACTH-INDEPENDENT
- Adrenocortical adenoma or carcinoma
- Iatrogenic: Supraphysiologic exogenous glucocorticoids
Low-dose dexamethasone test
- Dexamethasone (1 mg) is taken orally between 11 pm and midnight, and a single blood sample is drawn at 8 am the next morning
- Draw cortisol and dexamethasone level. (Dose is 0.3 mg/m2 in children.)
- Hypercortisolism is diagnosed if dexamethasone is detectable, and cortisol is NOT suppressed (i.e. cortisol level is high).
Late-night salivary cortisol concentration
- Patients collect saliva between 11 pm and midnight (passive drooling into a tube or chewing on a cotton).
- Sample can be kept at room temperature or refrigerated for several weeks before analyzed
High-dose dexamethasone suppression test (DST)
- Obtain baseline cortisol level, then give dexamethasone (2mg every 6 h) for 48 h
- Patients w/ adrenal hypercortisolism or ectopic ACTH syndrome do NOT exhibit decreased cortisol levels
- Decreased cortisol after DST = Cushing disease
CRH test
- 100 ug of ovine CRH (corticorelin) administered IV at time 0
- Cortisol and ACTH levels are measured every 15 min
- Patients with Cushing disease respond to CRH with a rise in cortisol and ACTH
- Patients with adrenal hypercortisolism or ectopic corticotropin syndrome (ECS) do NOT respond to CRH
What is the first line therapy of Cushing Syndrome?
Surgery (resection of the tumor), chemotherapy, or radiation
What are the pharmacotherapy for Cushing Syndrome that INHIBIT adrenal hormone synthesis?
- Ketoconazole
- Metyrapone
- Etomidate
Ketoconazole
- Drug Class: Antifungal agent, but Steroidogenesis inhibitor at higher dose
- MOA:
- Blocks production of cortisol and aldosterone
- Antiadrenergic activity within adrenal cortex
- Useful in adrenocortical carcinomas, breast/prostate cancer, and to reduce hirsutism and acne (in PCOS—adrenergic side effects)
- CYP3A4 inhibitor
What are the side effects of ketoconazole?
- **Elevation of hepatic transaminases/hepatotoxicity **
- N/V
- Can cause gynecomastia and hypogonadism in men
- Teratogenic