some review of kidney / adrenal physiology. the adrenals are endocrine organs that lie on top of the kidneys and are divided into the adrenal cortex and medulla. the adrenal medulla can be described as "a gland within a gland" and mostly secretes epinephrine, although nor-epinephrine and small amounts of dopamine are also secreted. the adrenal cortex is subdivided into three "zones", each secreting a different hormone- the zona glomerulosa secretes minerocorticoids such as aldosterone, zona fasiculata secretes glucocorticoids such as cortisol, and the zona reticularis secretes sex steroids such as DHEA, androgens, and small amounts of estrogen / cortisol.
addison's disease refers to adrenal hypofunction and can be primary or secondary. primary is due to damage to the adrenal cortex itself, usually due to autoimmune causes. this can result in decreased cortisol as well as aldosterone production, leading to hypoglycemia, hyponatremia, and hyperkalemia. the serum levels of ACTH will be extremely high but levels of cortisol will be extremely low in these patients. signs and symptoms might include weakness, dehydration, anorexia, hypotension, hyperpigmentation due to stimulation of melanocytes by ACTH. primary addison's can be confirmed with the ACTH stimulation test- patients with a damaged adrenal cortex will not respond to exogenous ACTH administration. secondary addison's is a shortage of ACTH, usually from damage to the pituitary from trauma, surgery, radiation, or tumors. this patient would have low levels of cortisol as well, but also low levels of ACTH and normal aldosterone secretion. also, because ACTH levels are low, melanocytes would not be stimulated and this results in hypopigmentation, contrasting with the hyperpigmentation seen in primary addison's.
an addisonian crisis results when a patient who has been taking exogenous glucocorticosteroids is unable to produce cortisol intrinsically due to lower ACTH levels when the glucocorticosteroids have been stopped. this patient may take weeks to months to acclimate, during which severe symptoms of weakness, nausea/vomiting, dehydration, hypoglycemia may occur.
cushing's syndrome is on the opposite side from addison's, representing adrenal hyperfunction. most cases are iatrogenic, from long term exogenous use of glucocorticosteroids. cushing's disease is a specific type which involves a pituitary adenoma that produces ACTH. ACTH may also be produced in ectopic cancer sites- lung cancer cells in particular. patients with cushing's will present with weight gain, especially around the abdomen, as well as moon facies, buffalo hump, and hypertension. aldosterone production may also be affected, leading to hypokalemia and hypertension as well. diagnosis can be confirmed by the dexamethasone test, in which the cortisol production in response to dexamethasone is measured-- normally it is suppressed, but in cushing's patients, it is unaffected.
conn's syndrome is hyperfunction of the adrenals specific to the zona glomerulosa- resulting in aldosterone hyperproduction. this generally results in hypertension and hypokalemia and is due to a adrenal adenoma. lab results might include high serum aldosterone, low potassium, and low renin (suppressed in response to high blood volume). a patient suspected of conn's might go through the aldosterone suppression test, in which IV fluid is introduced into the body and aldosterone levels are monitored-- if they are not inhibited as they should be in response to the extra fluid volume, they probably have conn's syndrome.
congenital adrenal hyperplasia is an underproduction of cortisol due to a deficiency of enzymes that regulate cortisol production. due to the shunting of cortisol precursor to androgen precursors such as 17-hydroxyprogesterone, these patients will have signs and symptoms of androgenism: hirsuitism, abnormal menses and infertility in females and precocious sexual development in males. they might also have short stature due to the premature closure of the epiphyseal growth plates. lab tests would look for increased levels of 17-ketosteroids and treatment involves exogenous administration of cortisol.
a pheochromocytoma is an catecholamine producing adenoma of the adrenal medulla which results in increased renin secretion, leading to severe hypertension which is resistant to blood pressure lowering regimens. the classic presentation is a patient with episodes of hypertension with intermittent episodes of hypotension, with headache, sweating, mental status changes, and hypermetabolism. a pheochromocytoma is generally diagnosed by the 24 hour urinary catecholamine test, meta-nephrine levels, and the clonidine suppression test.
questions
physiology...
1. what are the three zones of the adrenal cortex?
2. what do the cells of the adrenal medulla secrete?
3. what do the three zones of the adrenal cortex secrete?
4. describe the chain of production of ACTH.
addison's disease...
5. what is primary addison's disease?
6. what is the most common cause of primary addison's disease?
7. why might primary addison's lead to hypotension?
8. what are the signs and symptoms of primary addison's disease?
9. which areas of the body are more prone to developing hyperpigmentation in primary addison's?
10. what is the characteristic lab picture of a patient with primary addison's?
11. what are some other lab markers that might be abnormal in a patient with primary addison's?
12. what is the test that can be performed that will confirm the diagnosis of primary addison's?
13. what is the etiology of secondary addison's?
14. what is the sign that can differentiate secondary and primary addison's?
addisonian crisis...
15. what is an addisonian crisis?
16. what are the symptoms of an acute addisonian crisis?
cushing's syndrome...
17. what is the difference between cushing's syndrome and cushing's disease?
18. what are the causes of cushing's disease?
19. what is a potential cause for cushing's disease not related to the pituitary or adrenals?
20. what are the signs and symptoms for cushing's syndrome?
21. what are the lab findings for a patient with cushing's?
22. what is a test that can confirm the diagnosis of cushing's syndrome? how does it work?
conn's syndrome...
23. what is conn's syndrome?
24. what is the typical presentation of a patient with conn's syndrome?
25. what are the abnormal lab results of a patient with conn's syndrome?
26. what is a test that confirms the diagnosis of conn's syndrome?
congenital adrenal hyperplasia...
27. what is CAH?
28. what is the most common enzyme involved in CAH?
29. why might CAH lead to virilization?
30. how might CAH affect females?
31. how might CAH affect males?
32. why might CAH lead to short stature?
33. what is the lab test that can help diagnose CAH?
pheochromocytoma...
34. what is a pheochromocytoma?
35. what is the classic presentation of a patient with a pheochromocytoma?
36. what are the signs and symptoms of a patient with a pheohromocytoma?
37. what are the lab tests useful in diagnosing a pheochromocytoma?
38. what is a test that can be used to confirm the diagnosis of a pheochromocytoma?
answers
1. zona glomerulosa, fasiculata, reticularis.
2. mostly epinephrine, some nor-epinephrine, a little dopamine.
3. glomerulosa: minerocorticoids such as aldoesterone
fasiculata: glucocorticoids such as cortisol
reticularis: androgens such as DHEA
4. hypothalamus secretes CRH in response to stress, triggering pituitary to release ACTH, which acts on the adrenal glands.
5. adrenal insufficiency due to a damaged adrenal gland.
6. autoimmune destruction of the adrenal cortex.
7. because damage might include the zona glomerulosa, which would result in an underproduction of aldosterone, a hormone that facilitates water reabsorption in the kidneys.
8. WOAHH:
weakness
often dehydrated
anorexia
hypotension
hyperpigmentation / bronze skin
9. palmar creases, buccal mucosa, elbows and knees.
10. extremely low cortisol levels and high ACTH levels.
11. hypoglycemia, hyponatremia, hyperkalemia.
12. ACTH stimulation test: patients with primary addison's should not respond to administration of ACTH exogenously.
13. insufficient ACTH production by the anterior pituitary due to trauma, surgery, radiation, tumors.
14. secondary patients have pallor instead of hyperpigmentation because of low ACTH levels.
15. removal of long term exogenous administration of glucocorticoids leading to inability to produce cortisol due to low ACTH levels.
16. weakness
nausea/vomiting
dehydration
hypoglycemia
17. cushing's syndrome refers to adrenal hyperfunction generally whereas cushing's disease is a type of cushing's syndrome that refers to a pituitary adenoma.
18. generally from longterm exogenous administration of glucocorticoids.
19. ectopic sites that produce ACTH, such as lung cancer cells.
20. weight gain, especially mid abdominal
moon facies / buffalo hump
hypertension
21. hyperglycemia
secondary diabetes
hypertension / hypokalemia
22. 6 hour or overnight dexamethasone suppression test. normally cortisol production should be inhibited by administration of dexamethasone.
23. an increase in aldosterone production from an adrenal adenoma without cortisol increases.
24. hypertension.
25. high serum aldosterone
hypokalemia
low serum renin
26. aldosterone suppression test: administer extra IV fluid and watch for the lack of aldosterone suppression.
27. underproduction of cortisol due to deficiency of enzymes related to cortisol synthesis.
28. 21-hydroxylase.
29. because the decreased cortisol precursor production will lead to increased synthesis of other precursors, one of which is an androgen precursor, 17-hydroxyprogesterone.
30. symptoms of androgenism: hirsuitism, abnormal menses, infertility.
31. precocious development.
32. because high androgen levels also lead to premature closure of the epiphyseal growth plates.
33. serum levels of 17-ketosteroids such as 17-hydroxyprogesterone.
34. catecholamine producing tumor.
35. episodes of severe hypertension followed by hypotension.
36. headache
diaphoresis
mental status changes
hypermetabolism
postural hypotension
37. 24 hour urinary catecholamines and meta-nephrines
38. clonidine suppression test.
No comments:
Post a Comment