Endocrine Flashcards
Where is the drainage of the left adrenal vein?
Left renal vein
Where is the drainage of the right adrenal vein?
IVC
What is CRH?
Corticotropin-Releasing Hormone.
Released from anterior hypothalamus and causes released of ACTH from anterior pituitary
What is ACTH?
AndrenoCorticoTropic Hormone.
Released from anterior pituitary, which in turn causes adrenal glands to release cortisol
What feeds back to inhibit ACTH secretion?
Cortisol
What is Cushing’s syndrome?
Excessive cortisol production.
What is the most common cause of Cushing’s syndrome?
Iatrogenic (e.g. prednisone)
What is the second most common cause of Cushing’s syndrome?
Cushing’s disease
What is Cushing’s disease?
Cushing’s syndrome caused by excess production of ACTH by anterior pituitary
What is an ectopic ACTH source?
Tumor not found in the pituitary that secretes ACTH, which in turn causes adrenal gland to release cortisol without the normal negative feedback loop
What are the signs and symptoms of Cushing’s syndrome?
Truncal obesity, hirsutism, moon facies, acne, buffalo hump, purple striae, hypertension, diabetes, weakness, depression, easy bruising, myopathy
How can cortisol levels be indirectly measured over a short duration?
By measuring urine cortisol or 17-OHCS (breakdown product of cortisol)
What is a direct test of serum cortisol?
Serum cortisol level (highest in morning)
What initial tests should be performed in Cushing’s syndrome?
Electrolytes, serum cortisol, urine-free cortisol, urine 17-OHCS, low-dose dexamethasone suppression test
What is the low-dose dexamethasone suppression test?
Dexamethasone is a synthetic cortisol that results in negative feedback on ACTH secretion and subsequent cortisol secretion in healthy patients
After the dexamethasone suppression test, what is done next?
Check ACTH levels
Can plasma ACTH levels be checked directly?
Yes
In ACTH-dependent Cushing’s syndrome, how do you differentiate between a pituitary vs. an ectopic ACTH source?
High-dose dexamethasone test
What is the test for equivocal results for differentiating pituitary vs. ectopic ACTH tumor?
Bilateral petrosal vein sampling, especially with CRH infusion
What is the most common site of ectopic ACTH tumor?
66% are oat-cell tumors of the lung
How is adrenal adenoma treated?
Adrenalectomy (usually unilateral)
How is adrenal carcinoma treated?
Surgical excision (33% are operable)
How is an ectopic ACTH-producing tumor treated?
Surgical excision, if feasible
How is Cushing’s disease treated?
Transphenoidal adenomectomy
What medication must be given to a patient who is undergoing surgical correction of Cushing’s syndrome?
Cortisol (usually hydrocortisone until PO resumed)
What medications inhibit cortisol production?
Ketoconazole, metyrapone, aminoglutethimide, mitotane
What is the mechanism of action of ketoconazole?
Inhibits 11 beta-hydroxylase, c17-20 lyase, and cholesterol side-chain cleavage
What is the mechanism of action of aminoglutethimide?
Inhibits cleavage of cholesterol side chains
What is the mechanism of action of mitotane?
Inhibits 11 beta-hydroxylase and cholesterol side-chain cleavage
What is the mechanism of action of metyrapone?
Inhibits 11 beta-hydroxylase
What is a complication of bilateral adrenalectomy?
Nelson’s syndrome
What is Nelson’s syndrome?
Functional pituitary adenoma producing excessive ACTH and mass effect producing visual disturbances, hyperpigmentation, amenorrhea
What is an adrenal incidentaloma?
Tumor found in the adrenal gland incidentally on a CT scan
What is the incidence of adrenal incidentaloma?
4% of CT scans
What is the most common cause of adrenal incidentaloma?
Non-functioning adenoma
What is the differential diagnosis of adrenal incidentaloma?
Non-functioning adenoma, pheochromocytoma, adrenocortical carcinoma, aldosteronoma, metastatic disease, nodular hyperplasia
What is the treatment for adrenal incidentaloma?
Small/medium-sized: surgery controversial
Large (> 6 cm): resection
What are the indications for removal of adrenal incidentaloma less than 6 cm?
MRI T2 signal > 2, hyper-functioning tumor, enlarging cystic lesion, doesn’t look like adenoma
What tumor must be ruled out prior to biopsy or surgery for any adrenal mass?
Pheochromocytoma (24-hour urine for catecholamine, VMA, metanephrines)
What is pheochromocytoma?
Tumor of the adrenal medulla and sympathetic ganglion (from chromaffin cell lines) that produces catecholamines
Which age group is most likely to have pheochromocytoma?
Any age
What are the associated risk factors for pheochromocytoma?
MEN-II, family history, von Recklinghausen disease, von Hippel-Lindau disease
What are the signs and symptoms of pheochromocytoma?
- Palpitations
- Headache
- Episodic diaphoresis
Also, hypertension, anxiety, weight loss, tachycardia, hyperglycemia, polycythemia
How can the pheochromocytoma symptoms triad be remembered?
PHEochromocytoma:
Palpitations, Headache, Episodic diaphoresis
What is the most common sign of pheochromocytoma?
Hypertension
What is the differential diagnosis of pheochromocytoma?
Renovascular hypertension, menopause, migraine, carcinoid syndrome, preeclampsia, neuroblastoma, anxiety disorder with panic attacks, hyperthyroidism, insulinoma
What diagnostic tests should be performed for pheochromocytoma?
Urine screen: VMA, metanephrine, normetanephrine (breakdown products of catecholamines)
Urine/serum epinephrine, norepinephrine
What are the possible sites for pheochromocytoma?
Adrenal gland, organ of Zuckerkandl, thorax, bladder, scrotum
What are the pheochromocytoma localization tests?
CT, MRI, I-MIBG, PET scan, OctreoScan
What does I-MIBG stand for?
Iodine-131 MetaIodoBenzylGuanidine
How does the I-MIBG scan work?
I-MIBG is a norepinephrine analog that collects in adrenergic vesicles and, thus, in pheochromocytomas
What is the role of PET scan in pheochromocytoma?
Helpful in localizing pheochromocytomas that do not accumulate MIBG
What is the scan for imaging adrenal cortical pheochromocytoma?
NP-59 (a cholesterol analog)
What is the localizing option if a pheochromocytoma is not seen on CT, MRI or I-MIBG?
IVC venous sampling for catecholamines (gradient will help localize tumor)
What is the pheochromocytoma tumor site if epinephrine is elevated?
Must be adrenal or near the adrenal gland, because non-adrenal tumors lack the capability to methylate norepinephrine to epinephrine
What percentage of patients with pheochromocytoma have malignant tumors?
10%
Can histology be used to determine malignancy of a pheochromocytoma?
No; only distant metastasis or invasion
What is the classic pheochromocytoma “rule of 10”?
10% malignant 10% bilateral 10% in children 10% multiple tumors 10% extra-adrenal
What is the preoperative/medical treatment for pheochromocytoma?
Increase intravascular volume with alpha-blockers (e.g. phenoxybenzamine, prazosin) to allow reduction in catecholamine-induced vasoconstriction and resulting volume depletion.
Treatment should start as soon as diagnosis is make.
What is the surgical treatment for pheochromocytoma?
Tumor resection with early ligation of venous drainage and minimal manipulation (lower possibility of catecholamine crisis)
What are the possible perioperative complications of pheochromocytoma surgery?
Hypertensive crisis with manipulation (treat with nitroprusside); hypotension with total removal of tumor; cardiac dysrhythmias
In the patient with pheochromocytoma, what must be ruled out?
MEN-II
What is the organ of Zuckerkandl?
Body of embryonic chromaffin cells around the abdominal aorta (near IMA).
Normally atrophies during childhood, but is the most common site of extra-adrenal pheochromocytoma