Adrenal Disorders Flashcards
What are the primary functions of the glucocorticoids?
protects against stress and affects protein and carbohydrate metabolism. Think cortisol.
What are the primary functions of the mineralcorticoids?
regulates the retention and excretion of fluids and electrolytes (especially Na and K) by the kidneys.
Think aldosterone.
What are the primary functions of the adrenal androgens?
Pubertal growth of body hair. Exert little effect on sexual function. Think DHEA (dehydroepiandrosterone)
What are chromaffin cells?
main source of catecholamines in the adrenal medulla
What effect can cortisol have on the adrenal medulla?
Cortisol produced in the adrenal cortex that reaches the medulla in high levels causes up regulation in the production of epinephrine
What are the effects of epi and norepi on the cardiovascular system?
Strengthens the contractility of the myocardium. (Beta1 action, inotropic action). Increases rate of contraction (Beta1 action, chronotropic action). Constricts arterioles in the skin (Alpha1 action). Dilates vessels to liver and skeletal muscle (Beta2 action)
What are the effects of epi and norepi on the respiratory system?
bronchodilation by acting directly on bronchial smooth muscle (Beta2 action). relieves all known allergic- or histamine-induced bronchoconstriction in anaphylactic shock
What is a pheochromocytoma?
tumor derived from neural crest cells of the sympathetic nervous system that causes episodic symptoms (palpitations, sweating, HA, fainting, HTN) because it releases catecholamines
What is the 90% rule of pheochromocytomas?
90% of the time they arise from the adrenal medulla, 90% are unilateral, 90% aren’t malignant, 90% occur in adults
How is a pheochromocytoma diagnosed?
H/P. elevated urinary excretion of catecholamines or their metabolites (metanephrines and vanillylmandelic acid) DURING a period of HTN. CT of abdomen or MRI
What is the function of aldosterone?
Increases sodium (Na) and water reabsorption by the kidneys AND increases the secretion of potassium (K), thereby indirectly regulating blood volume and blood pressure
Describe the renin-angiotensin-aldosterone system of the kidneys.
Fall in blood pressure –> juxtaglomerular cells secrete renin. Renin converts angiotensinogen to angiotensin I which is converted to angiotensin II in the lungs. Angiotensin II constricts blood vessels and stimulates the adrenal cortex to secrete aldosterone reducing urine output and increasing BP by increasing blood volume
What are the specific immunologic and antiinflammatory effects of cortisol?
Suppresses immune response by reducing humoral and cell-mediated immunity. Exogenous steroids block inflammation by decreasing capillary permeability and stabilizing lysosomal membranes so inflammatory mediators are not released. blocks release of arachidonic acid, the precursor of prostaglandins and leukotrienes
What are adverse effects of excess glucocorticoids?
hyperglycemia, suppresses the immune system, decreased bone density, CNS psychosis, HTN, stimulate gastric acid and pepsin production
What is Cushing’s syndrome?
prolonged exposure to excessive glucocorticoid hormones that’s either endogenous (ACTH dependent-Cushings disease or ACTH independent-adrenal adenoma/carcinoma) or exogenous (excessive steroid administration)
What is Cushing’s disease?
excessive production of ACTH from a pituitary tumor or ectopic sources of ACTH from small cell lung cancer
What is the most direct and reliable index of cortisol secretion?
24-hour urinary cortisol excretion. Should be performed in a nonstressful outpatient setting. Urine creatinine should be measured as well to confirm an adequate 24-hour collection
What diagnostic tests/tools might be useful if a patient is found to have elevated urinary cortisol?
Plasma ACTH (recommended measurement between midnight and 2AM). Abdominal CT scan (looking for adrenal mass). MRI of the sella for pituitary tumor
What is the dexamethasone suppression test?
1mg dexamethasone (a steroid) given orally in the evening. Serum cortisol determination at about 8am the next AM. HPA axis should be suppressed with normal physiology
What is primary adrenal insufficiency?
Addison’s disease: Most common cause of adrenal insufficiency. Results from destruction or dysfunction of the adrenal cortex. Glucocorticoid and mineralocorticoid secretion is reduced. May be fatal if untreated
What is secondary adrenal insufficiency?
Results from inadequate stimulation of adrenal cortex by ACTH. Usually occurs after discontinuation of exogenous steroids that cause prolonged suppression of the HPA (Hypothalamic-pituitary-adrenal) axis
What is the clinical presentation of adrenal insufficiency?
hypotension, weight loss, fatigue, vomiting, diarrhea, anorexia, muscle/jt pain, abdominal pain, postural dizziness
Why is hyperpigmentation a common presentation with Addison’s disease?
Decreased levels of cortisol means less inhibition of HPA axis. The leads to increased proopiomelanocortin (POMC) synthesis. POMC contains melanocyte-stimulating hormone (MSH) fragments. When POMC levels are increased, so are levels of MSH, leading to pigmentation of the skin
Why is salt craving a common presentation with Addison’s disease?
low secretion of aldosterone leads to hyponatremia and salt craving
