absite review endocrine - Sheet1 Flashcards
(234 cards)
1
Q
What percentage of T3 is derived from conversion of T4?
A
80%.
2
Q
❍ What is the major thyroid hormone-binding protein?
A
Thyronine-binding globulin (TBG).
3
Q
❍ What percentage of T4 and T3 are bound?
A
Greater than 99.5%.
4
Q
❍ What is the major cause of a decreased T3 concentration in patients with a critical illness?
A
Impaired peripheral conversion of T4 to T3 secondary to inhibition of the deiodination process.
5
Q
❍ What factors decrease TSH secretion?
A
Acute and chronic illness, adrenergic agonists, calorie restriction, dopamine and dopamine agonists, surgical stress, and thyroid hormone metabolites. Minor decreases occur with carbamazepine, clofibrate, opiates, phenytoin, and somatostatin.
6
Q
❍ A patient with a history of radiation exposure as a child was found to have an enlarged lymph node on physical examination. The lymph node is removed, and there is normal-appearing thyroid tissue in the lymph node. What is the diagnosis?
A
Papillary thyroid cancer. Treatment is total thyroidectomy, ipsilateral modified radical neck dissection, and postoperative ablative I-131 therapy. Bilateral neck dissection is reserved for clinically apparent bilateral nodal disease.
7
Q
❍ Name some negative prognostic variables for papillary thyroid carcinoma.
A
Age >70 years, vascular/lymphatic tumor invasion, high-grade tumor, and extrathyroid capsular extension.
8
Q
❍ What is the embryologic origin of the thyroid gland?
A
From median downgrowth of the first and second pharyngeal pouches in the area of the foramen cecum.
9
Q
❍ What is the embryologic origin of the parafollicular cells?
A
From the ultimobranchial bodies of the fourth and fifth branchial pouches. Neuroendocrine cell lineage.
11
Q
❍ What is the effect of pressor doses of dopamine on TSH regulation?
A
It decreases TSH levels to normal in patients with preexisting hypothyroidism.
13
Q
❍ What accounts for the low T4 state seen in critically ill patients?
A
A decrease in the binding of T4 to serum protein carriers, decreased TSH level, decreased production of T4, and an increase in the nondeiodinative pathways of T4 metabolism.
16
Q
❍ What is the free T4 index (FTI)?
A
FTI = total T4 × T3 resin uptake.
17
Q
❍ What genetic mutation is associated with medullary thyroid cancer?
A
RET proto-oncogene.
18
Q
❍ What is the first test after H+P to evaluate a thyroid nodule?
A
Fine needle aspiration (FNA).
19
Q
❍ Can radioactive iodine be given safely in pregnancy?
A
No.
20
Q
❍ What signs and symptoms are associated with hypothyroidism?
A
Decreased mental acuity, hoarseness, somnolence, cold intolerance, dry skin, brittle hair, weight gain, hypothermia, generalized edema, hypoventilation, sinus bradycardia, and, possibly, hypertension.
23
Q
❍ T/F: Cardiac output (CO) is decreased in hypothyroidism..
A
TRUE
24
Q
❍ What are the causes of alveolar hypoventilation in myxedematous hypothyroid patients?
A
Respiratory center depression with decreased CO2 sensitivity, defective respiratory muscle strength, and possible airway obstruction caused by tongue enlargement.
27
Q
❍ What laboratory abnormalities are associated with hypothyroidism?
A
Hyponatremia, hypoglycemia, hypercholesterolemia, and a normochromic normocytic anemia.
29
Q
❍ What hormone should uniformly be given with thyroid replacement in the hypothyroid myxedematous patient?
A
Hydrocortisone.
31
Q
❍ When calcium is difficult to replace post parathyroidectomy with vitamin D and calcium alone, what electrolyte abnormality should be sought?
A
Hypomagnesemia. Low magnesium induces skeletal muscle resistance to PTH.
34
Q
❍ What electrolyte ratio is pathonomonic for hyperparathyroidism?
A
Serum chloride to phosphate ratio >30.
35
Q
❍ What are the hemodynamics of thyroid storm?
A
Tachycardia, increased CO, and decreased systemic vascular resistance (SVR).
37
Q
❍ What muscle of the larynx is not innervated by the recurrent laryngeal nerve?
A
Cricothyroid—innervated by superior laryngeal nerve.
38
❍ What artery do all the parathyroids typically receive their blood supply from?
Inferior thyroid.
39
❍ Which oncogene is hyperparathyroidism associated with?
Prad oncogene.
40
❍ What is the utility of intraoperative parathyroid hormone assays?
A 50% drop in serum PTH at 5 minutes post offending gland removal vs. preoperative value confirms therapeutic resection.
43
❍ What bone finding is pathognomonic finding for hyperparathyroidism?
Osteitis fibrosa cystica.
44
❍ T/F: Hyperparathyroid is most commonly associated with four-gland hyperplasia.
False. Solitary parathyroid adenoma is the most common etiology.
45
❍ What are the ophthalmologic signs of hyperthyroidism?
Exophthalmos, lid lag, lid retraction, and periorbital swelling.
46
❍ What laboratory findings are associated with hyperthyroidism?
Hypercalcemia, hypokalemia, hyperglycemia, hypocholesterolemia, microcytic anemia, lymphocytosis, granulocytopenia, hyperbilirubinemia, and increased alkaline phosphatase.
49
❍ What is the initial treatment of thyroid storm?
Intravenous fluids, hypothermia, acetaminophen, propanolol, propylthiouracil (PTU), and iodine.
51
❍ What are the CNS manifestations of myxedema?
Depression, memory loss, ataxia, frank psychosis, myxedema, and coma.
53
❍ What is the mechanism of hyponatremia in hypothyroidism?
Impaired water excretion related to decreased delivery of sodium and volume to the distal renal tubules secondary to decreased renal blood flow.
55
❍ What are the common causes of hypothyroidism?
Cessation of thyroid medication, autoimmune thyroid disease, decreased TSH, radioactive and surgical ablation, and iodine deficiency/excess.
58
❍ What is the first thyroid function test abnormality seen in patients with hypothyroidism?
TSH elevation (usually associated with a low T4).
59
❍ What single test would allow for the differentiation of thryotoxicosis from acute destructive viral thryoiditis?
A radioactive iodine uptake (RAIU) test.
60
❍ Why is the pulse pressure wide in patients with thyrotoxicosis?
Increased blood flow and vasodilatation.
61
❍ What inhibits the release of TSH?
Elevated circulating levels of T3, T4, and somatostatin.
63
❍ A 45-year-old female presents with a 2-year history of diffuse, tender thyroid enlargement; lethargy; and a 20-pound weight gain. What is the most likely diagnosis?
Hashimoto’s thyroiditis.
65
❍ What is the appropriate treatment for Hashimoto’s thyroiditis?
Thyroid replacement therapy.
66
❍ How is TSH deficiency diagnosed?
Simultaneous measurement of basal serum TSH and thyroid.
68
❍ What test is used to distinguish a hypothalamic defect from a pituitary defect in a patient with hypothyroidism?
The TRH stimulation test.
70
❍ What is the appropriate treatment for patients with thyroglossal duct cysts?
Excision of the entire cyst, as well as the thyroglossal tract to its origin, at the foramen cecum, including the central portion of the hyoid bone.
73
❍ What is the venous drainage of the thyroid gland?
The superior and middle thyroid veins drain into the internal jugular vein and the inferior thyroid veins drain into the innominate vein.
76
❍ What is the result of unilateral injury to the recurrent laryngeal nerve?
Hoarseness.
78
❍ What is the most common location of the recurrent laryngeal nerve?
In the tracheoesophageal groove.
79
❍ What is the result of bilateral injury to the superior laryngeal nerve?
Swallowing disorders.
81
❍ What is the mechanism of action of PTU?
PTU interferes with the incorporation of iodine into the tyrosine residues of thyroglobulin, preventing oxidation of iodide to iodine. It also inhibits the peripheral conversion of T4 to T3 and is contraindicated in pregnancy.
84
❍ What is the definitive, nonsurgical treatment for Grave’s disease?
I-131 radioablation.
86
❍ FNA of a 6-year-old child with a solitary thyroid nodule is benign. What is the next recommended step?
Open surgical biopsy given the high false-negative rate of FNA in children, in whom 50% of cold nodules are malignant.
88
❍ What are the indications for surgical treatment of Grave’s disease?
Extremely large glands, presence of nodules, women of childbearing age, and patients who are opposed to radioiodine.
91
❍ What is the preferred treatment for patients with toxic multinodular goiter?
Thyroid resection (lobectomy to total thyroidectomy) because I-131 treatment often requires repeated doses, does not reduce goiter size, and may even cause acute enlargement. Surgical resection avoids airway obstruction, esophageal dysfunction, recurrent nerve compression, SVC syndrome, and malignant transformation.
93
❍ A 35-year-old female presents with a diffuse, slowly growing goiter, weight gain, fatigue, and cold intolerance. What is the most likely diagnosis?
Hashimoto’s thyroiditis.
95
❍ What is the single most important test in the diagnostic workup of a patient with a solitary thyroid nodule?
FNA.
96
❍ For which thyroid malignancy does radiation exposure increase the incidence?
Papillary cell CA.
97
❍ What is Hurthle cell carcinoma?
A variant of follicular cell CA. Size is the only predictor of malignancy when Hurthle cells are seen on FNA (resection is Tx). Malignancy is defined by histological invasion of cells into thyroid capsule or vessels. Hurthle cell CA is associated with a history of Hashimoto’s thyroiditis.
99
A 44-year-old male presents with a 5-cm thyroid nodule. FNA returns fluid, the nodule disappears, and the cytology is benign. What is the next step in management?
Total thyroid lobectomy with isthmusectomy should be considered because there is an increased chance of malignancy in large cysts of this size (>3 cm).
102
❍ A 56-year-old male with no risk factors presents with a thyroid nodule. The FNA is nondiagnostic (follicular cells). What is the treatment of choice?
Thyroid lobectomy with isthmusectomy. If final pathology reveals follicular carcinoma, secondary surgery for completion total thyroidectomy with postoperative ablative I-131 is indicated.
104
❍ What percentage of patients with usual papillary carcinoma (greater than 1 cm) are found to have multicentric disease on pathologic examination of the entire thyroid?
70% to 80%.
106
❍ What percentage of patients with papillary carcinoma have cervical lymph node involvement?
30%.
107
❍ What factor best correlates with the presence of lymph note metastases in papillary carcinoma?
Age.
108
❍ What is the treatment of choice for patients with papillary thyroid cancer without clinical evidence of lymph node metastasis?
Total thyroidectomy.
110
❍ A patient is noted to have a very high calcium and a palpable rock hard neck mass. What is your diagnosis?
Parathyroid adenocarcinoma; Tx: wide excision with en block resection of adjacent thyroid tissue.
111
❍ Classify the MEN syndromes.
MEN 1—PPP—pancreatic neuroendocrine tumors, pituitary adenoma, hyperparathyroidism (four gland hyperplasia, not adenoma) MEN 2a—medullary thyroid, pheochromocytoma, and hyperparathyroidism MEN 2b—medullary thyroid, pheo, and mucosal neuromas/marfan syndrome. All three exhibit autosomal-dominant inheritance. MEN 1 is associated with a chromosome 11 tumor-suppressor gene mutation and is also associated with an increased risk of carcinoid tumors.
115
❍ Characterize carcinoid tumors.
Neuroendocrine cell etiology. Can occur throughout the GI tract or bronchi. Carcinoid syndrome characterized by flushing, diarrhea, and right-sided heart failure most commonly occurs with metastatic disease and mid-gut tumors. Treatment for syndrome or metastasis is octreotide. Isolated mets can be resected.
117
❍ A 36-year-old female presents with a 3-cm papillary carcinoma and no clinical evidence of lymph node involvement. She was treated with a total thyroidectomy. What adjuvant therapy is indicated?
TSH suppression with thyroid hormone, radioiodine ablation with I-131, follow-up scan 6 months after ablation with thyroglobulin levels, and physical examination.
120
❍ Follicular carcinoma metastases occur primarily by what route?
Hematogenous dissemination to the lungs, bones, and other peripheral tissues.
122
❍ How is the pathologic diagnosis of follicular thyroid carcinoma confirmed?
Identification of vascular or capsular invasion by the tumor from histologic sections.
123
❍ What are the indications for adjuvant thyroid hormone in patients with well-differentiated thyroid carcinoma?
All patients with well-differentiated carcinoma should be treated with thyroid hormone to suppress TSH for life, regardless of the extent of their surgery.
125
❍ What is the surgical treatment for medullary thyroid carcinoma (MTC)?
Total thyroidectomy with central node dissection, lateral cervical lymph node sampling of palpable nodes, and a modified radical neck dissection, if positive.
128
❍ A germline defect in what gene is responsible for multiple endocrine neoplasias (MEN 2a and 2b) and familiar medullary thyroid carcinoma (FMTC)?
The RET proto-oncogene. Patients with this mutation should undergo prophylactic thyroidectomy before the age of 10 years.
130
❍ T/F: Exposure to low-dose radiation therapy is considered a risk factor for thyroid carcinoma.
True.
131
❍ What are the histochemical characteristics of MTC?
Congo red dye positive, apple-green birefringence consistent with amyloid, immunohistochemistry positive for cytokeratins, CEA, and calcitonin. Parafollicular C cells are the precursor to tumor cells.
134
❍ A patient with MTC has a high urinary vanillylmandelic acid (VMA) and an enlarged left adrenal gland. What is the next step in management?
Medical management with alpha- and beta-blockers, if necessary, followed by resection of the left adrenal gland. This should be performed before the thyroid surgery.
136
❍ What is the embryological origin of the parathyroid glands?
The inferior parathyroid glands originate from the third pharyngeal pouch, and the superior parathyroid glands originate from the fourth pharyngeal pouch.
139
❍ What is the arterial blood supply to the parathyroids?
It is usually from the inferior thyroid artery. Occasionally, it can arise from the superior thyroid artery, thyroid ima artery or arteries in the larynx, esophagus, or mediastinum.
142
❍ Where are the inferior parathyroids located?
They are usually more ventral than the superior glands and lie close to or within that portion of the thymus gland that extends from the inferior pole of the thyroid gland into the chest. They are typically located inferior to the junction of the inferior thyroid artery.
145
❍ What are the etiologies of hypercalcemia?
Hyperparathyroidism, paraneoplastic syndrome, metastatic CA, bone metastasis, milk–alkali syndrome, and sarcoidosis.
147
❍ What is the effect of PTH on the intestinal absorption of calcium?
PTH stimulates vitamin D hydroxylation in the kidney and increases intestinal absorption of calcium.
149
❍ Where is calcitonin produced?
In the parafollicular cells (C cells) of the thyroid.
151
❍ What are the laboratory findings in familial hypocalciuric hypercalcemia?
Low urine calcium (normal or high in hyperparathyroidism), hypermagnesemia, hypercalcemia. Associated with autosomal-dominant inheritance.
154
❍ A 48-year-old male has a serum calcium of 13 mg/dL and a serum PTH of 400 mEq/mL. What is the most likely diagnosis?
Primary hyperparathyroidism.
156
❍ A 35-year-old female has a serum calcium of 8.5 mg/dL, a serum PTH of 400 mEq/mL, and a serum creatinine of 5.6 mg/dL. What is the most likely diagnosis?
Secondary hyperparathyroidism.
158
❍ What are the indications for parathyroid exploration in patients with asymptomatic or minimally symptomatic hyperparathyroidism?
1. Age less than 50 years. 2. Markedly elevated serum calcium. 3. History of an episode of life-threatening hypercalcemia. 4. Decreased creatinine clearance. 5. Nephrolithiasis. 6. Markedly elevated 24-hour urinary calcium excretion. 7. Substantially decreased bone mass. 8. The patient requests surgery. 9. Poor follow-up expected. 10. Coexistent illness complicating conservative management.
167
❍ T/F: After successful surgical treatment of parathyroid pathology, renal stone formation rate returns to that of patients with a history of idiopathic renal stone formation history (30%).
True.
170
❍ What percentage of patients with primary hyperparathyroidism have a single adenoma?
80%.
172
❍ During exploration for primary hyperparathyroidism, three normal parathyroid glands are found but the fourth cannot be identified. What is the next step in management?
Extend the exploration through the existing incision, to include the central neck between the carotids, posteriorly to the vertebral body, superiorly to the level of the pharynx and carotid bulb, and inferiorly into the mediastinum.
175
❍ What intraoperative modality may assist in locating an intrathyroidal parathyroid gland?.
Ultrasound
176
❍ What is the appropriate management if the fourth parathyroid gland cannot be located by intraoperative ultrasound?
Terminate the operation for localization studies.
178
❍ What voice problem will a patient have if there is injury to external branch of superior laryngeal nerve?
Loss of high-pitched tone.
179
❍ What is the most reliable method of differentiating a parathyroid adenoma from parathyroid hyperplasia?
Visual inspection of all four parathyroid glands.
180
❍ What are the components of the MEN 1 syndrome?
Parathyroid hyperplasia (90%), islet cell neoplasms (30%–80%), and pituitary tumors (15%–50%).
182
❍ What is the treatment of choice for patients with hyperparathyroidism associated with MEN 1 or MEN 2?
Subtotal (three and a half gland) parathyroidectomy or total parathyroidectomy with autotransplantation in the forearm.
184
❍ What is the treatment of choice for patients with parathyroid carcinoma?
Radical resection of the involved gland, the ipsilateral thyroid lobe, and the regional lymph nodes.
186
❍ What preoperative studies should be performed prior to reoperation for persistent or recurrent hyperparathyroidism?
A 24-hour urinary calcium excretion to rule out familial hypocalcemic hypercalcemia. Sestamibi is the localization study of choice.
188
❍ A 25-year-old pregnant female, in her second trimester, presents with hyperparathyroidism and a serum calcium of 12 mg/dL. What is the treatment of choice?
Prompt parathyroid exploration.
190
❍ What is the surgical treatment of choice for patients with secondary hyperparathyroidism?
Subtotal (three and a half ) parathyroidectomy or total parathyroidectomy with autotransplantation in the forearm.
192
❍ What is the first-line therapy for patients with marked hypercalcemia and/or severe symptoms?
Intravenous hydration followed by furosemide.
194
❍ What are the indications for calcium supplementation after thyroid or parathyroid surgery?
Circumoral paresthesias, anxiety, positive Chvostek’s or Trousseau’s sign, tetany, ECG changes, or serum calcium less than 7.1 mL/dL.
196
❍ What is the immediate treatment for patients with acute symptomatic hypocalcemia?
Intravenous calcium gluconate.
197
❍ In a nonacute setting, what is the maximum useful amount of calcium supplementation?
2 g of calcium/d.
198
❍ What is the appropriate calcium supplementation if the maximum amount of calcium has already been given and the patient is still hypocalcemic?
Calcitriol or other vitamin D preparations should be added, if necessary.
200
❍ What are the phenotypic abnormalities seen in patients with MEN 2b?
MTC, pheochromocytoma, mucosal neuromas, ganglioneuromas, and a marfanoid habitus.
202
❍ What zone of the adrenal gland is spared in autoimmune adrenal disease?
The medulla.
203
❍ Secretion of which adrenal hormone is not impaired by secondary adrenal insufficiency?
Aldosterone.
204
❍ What is the most common cause of chronic primary adrenal insufficiency (Addison’s disease)?
Autoimmune disease.
205
❍ What are the most common causes of acute secondary adrenal insufficiency?
Steroid medication withdrawal, Sheehan’s syndrome (postpartum pituitary necrosis), bleeding into a pituitary macroadenoma, and head trauma.
208
❍ What diseases produce a slow, insidious progression to primary adrenal insufficiency?
Autoimmune diseases, tuberculosis, systemic fungal infections, CMV, Kaposi’s sarcoma, metastatic carcinoma, and lymphoma.
211
❍ What does the posterior pituitary secrete?
ADH and oxytocin.
212
❍ What does the anterior pituitary secrete?
Growth hormone (GH), adrenal corticotropin hormone (ACTH), TSH, leutinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin.
214
What vision changes will lead one to suspect a pituitary mass?
Bilateral hemianopsia.
216
❍ What therapy should be instituted prior to obtaining the results of an ACTH stimulation test in a critically ill patient?
An empiric stress dose of dexamethasone.
218
❍ How can the ACTH stimulation test be normal in secondary adrenal insufficiency?
If the gland has not yet atrophied, it retains the ability to be stimulated.
219
❍ What is the basis of the insulin-induced hypoglycemia test for patients with secondary adrenal insufficiency?
Hypoglycemia induced by 0.1 units of insulin/kg stimulates the entire hypothalamus–hypophyseal–adrenal axis (HPA) and the sympathetic nervous system. Plasma cortisol levels should exceed 20 g/dL.
221
❍ What is the short metyrapone test?
Metyrapone inhibits adrenal 11-hydroxylase. Normally the cortisol precursor, 11-deoxycortisol, increases to at least 7 g/dL. This is in response to the decreased production of cortisol and loss of the negative feedback of cortisol to the HPA axis, hence stimulation of ACTH. This is indicative of secondary adrenal insufficiency only in the setting of a previously measured cortisol level of 8 g/dL.
223
❍ After an endocrinologic diagnosis has been established by hormonal studies, what is the radiologic study of choice to assess for a pituitary or hypothalamic tumor?
MRI with analysis of the sagittal and coronal sections. A CT scan can be helpful if bony invasion is suspected.
225
❍ What is the emergent steroid replacement for patients with adrenal insufficiency?
50–100 mg of intravenous hydrocortisone every 8 hours.
226
❍ What type of patients should receive fluorocortisone?
Those with primary adrenal insufficiency.
227
❍ What is the characteristic hemodynamic pattern of adrenal insufficiency?
Decreased SVR. Clinically, hypotension with a high CO, normal filling pressures, and hypoglycemia are seen.
229
❍ When do the serum corticotropin and cortisol concentrations return to normal following routing surgery?
Within 24–28 hours.
231
❍ What diagnostic test is the best predictor of adrenal adequacy in patients previously receiving steroids, who are scheduled for surgery?
The peak cortisol level after administration of corticotropin.
234
❍ What are the adverse effects of excessive cortisol dosing for high stress situations?
The catabolic effects on muscle, impaired wound healing, inhibition of insulin, and the anti-inflammatory effect on active infection.
236
❍ What are the current recommendations for stress doses of cortisol in patients with suspected adrenal insufficiency?
Minor stress, 25 mg/d; moderate stress, 50–75 mg/d; and major stress, 100–150 mg/d.
238
❍ What is the flow phase of the metabolic response to stress?
It occurs approximately 24 hours after injury and is characterized by a rise in CO, temperature, oxygen consumption, and serum insulin levels.
241
❍ A 45-year-old male develops hypotension and lethargy and has a hemoglobin of 12 g/dL and a blood glucose of 34 mg/dL 24 hours after colectomy. His history is significant for a renal transplant 3 years ago. What is the most likely diagnosis?
Addisonian crisis.
243
❍ What inhibits GH secretion?.
Somatostatin
244
❍ Where does aldosterone exert its primary effect?
On the distal tubules and collecting ducts of the kidney.
246
❍ What is the effect of aldosterone on the kidney?
It increases the absorption of sodium from the urine in exchange for potassium, thereby aiding in water retention and restoring intravascular volume.
249
❍ What are the metabolic effects of catecholamines during periods of stress?
Increased glycogenolysis, gluconeogenesis, lipolysis and ketogenesis, and inhibition of insulin use in peripheral tissues.
252
❍ What are the functions of angiotensin II?
Vasoconstriction, cardiac stimulation, and stimulation of ADH, aldosterone, and thirst.
254
❍ What stimuli cause release of ADH (vasopressin)?
Plasma osmolality greater than 285 mOsm/L, decreased circulating blood volume, catecholamines, the renin–angiotensin system, and opiates.
257
❍ What inhibits release of LH in the adult male?
Androgens synthesized by the testes.
259
❍ What is the function of FSH in the adult female?
It stimulates maturation of the Graafian follicle and production of estradiol.
261
❍ What limits the secretion of ACTH and corticotropin-releasing factor (CRF)?
Circulating levels of ACTH.
262
❍ GH is released in bursts at what specific times?
3–4 hours after meals and during stage III and IV sleep.
264
❍ What inhibits the release of prolactin?.
Dopamine
265
❍ What is the main physiological stimulus for prolactin release?
Suckling of the breast.
266
❍ Which drugs interfere with release of dopamine into the pituitary portal circulation and enhance prolactin secretion?
Metaclopramide, haloperidol, chlorpromazine, and reserpine.
268
❍ What signs and symptoms, related to enlargement of the gland, are associated with a pituitary neoplasm?
Visual field defects (bitemporal hemianopsia), abnormal extraocular muscle movements, and spontaneous CSF rhinorrhea.
270
❍ What characteristics of pituitary apoplexy are caused by hemorrhage?
Severe headache, sudden visual loss, meningismus, decreased sensorium, bloody CSF, and ocular palsy.
272
❍ What is included in the differential diagnosis of a sellar or parasellar tumor?
Pituitary adenoma, craniopharyngioma, parasellar meningioma, sarcoidosis, metastatic lesions, and gliomas.
274
❍ In evaluation of a patient with an ACTH deficiency, what test will distinguish a hypothalamic CRH deficiency from a pituitary ACTH deficiency?
The CRH stimulation test.
276
❍ What is the diagnosis if there is absence of ACTH responsiveness to CRH?
A pituitary corticotropin deficiency.
277
❍ What is the ACTH stimulation test used to evaluate?
The capacity of the adrenal glands to secrete cortisol.
278
❍ What two tests will stimulate the entire HPA?
The insulin-induced hypoglycemia test and the glucagon test.
281
❍ What condition is defined by a relative or absolute insufficiency of vasopressin secretion from the posterior pituitary?
Diabetes insipidus (DI).
284
❍ How is the diagnosis of central DI confirmed?
By the water deprivation test.
285
❍ What is the treatment of choice for central DI?
Administration of exogenous vasopressin.
286
❍ T/F: Vasopressin aids in the treatment of renal DI..
FALSE
287
❍ What are the clinical characteristics of Sheehan’s syndrome?
Postpartum failure to lactate, postpartum amenorrhea, and progressive signs and symptoms of adrenal insufficiency and hypothyroidism.
290
❍ What are the most common types of pituitary adenomas?
Prolactin-secreting and null-cell (chromophobe adenoma).
291
❍ What is the most common functional pituitary tumor?.
Prolactinoma
292
❍ What is the most common presenting symptom of prolactinomas in females?
Secondary amenorrhea.
293
❍ What percentage of patients with a prolactinoma and secondary amenorrhea have an associated galactorrhea?
50%.
294
❍ What pharmaceutical agent is effective in reducing serum prolactin, reducing tumor mass, and inhibiting tumor growth?
Bromocriptine (a dopaminergic agonist).
296
❍ What is the etiology of Cushing’s disease?
Hypersecretion of ACTH by the pituitary.
297
❍ What is the most likely diagnosis in a patient with Cushing’s syndrome and a low plasma ACTH level?
An adrenal tumor.
298
❍ T/F: Most patients with Cushing’s disease harbor microadenomas that lend themselves to complete surgical resection.
True.
301
❍ What is the etiology of post-traumatic persistent hyperglycemia?
Persistent high cortisol levels.
303
❍ What is the most common cause of excess GH secretion?
A GH-secreting pituitary adenoma.
304
❍ What metabolic manifestations are associated with acromegaly?
Hypertension, diabetes mellitus, goiter, and hyperhidrosis.
306
❍ What test confirms the diagnosis of acromegaly?
The glucose suppression test. (An oral administration of 100 g of glucose fails to suppress the GH level to less than 5 ng/mL at 60 minutes.)
309
❍ What is the treatment of choice for patients with a GH-producing pituitary adenoma?
Surgical excision.
310
❍ What is the appropriate treatment for a patient with a GH-producing pituitary adenoma who cannot withstand the surgical procedure?
Long-term treatment with octreotide.
312
❍ What are the most important hormones to evaluate, prior to surgical excision of a pituitary adenoma, to avoid potential perioperative catastrophe?
Cortisol and thyroid levels.
314
❍ What is the best surgical approach to the pituitary?
The transnasal, trans-sphenoidal approach.
315
❍ What is the most common cause of surgical death with the transnasal, trans-sphenoidal approach?
Direct injury to the hypothalamus, with delayed mortality attributed to CSF leaks and their attendant septic complications or secondary to vascular injury.
317
❍ What are the contraindications to the trans-sphenoidal approach?
Extensive lateral tumor herniating into the middle fossa with minimal midline mass, ectatic carotid arteries projecting toward the midline, and acute sinusitis.
320
❍ What is the standard dosing regimen of glucocorticoids given to all patients undergoing surgical excision of a pituitary tumor?
40 mg of intravenous methylprednisolone (or 10 mg dexamethasone) every 6 hours, usually starting the day prior to surgery and continuing for 1 or 2 days postoperatively, followed by a tapering dose regimen.
322
❍ A 55-year-old female is in the ICU 1 day after pituitary tumor resection when she suddenly develops loss of vision. What is the treatment of choice?
Emergent trans-sphenoidal re-exploration.
325
❍ What is the treatment of choice for a patient with a pituitary tumor who is a poor surgical candidate?
4000 cGy radiation therapy.
327
❍ What is the recurrence rate of pituitary tumors treated with radiation therapy?
50%.
328
❍ A 51-year-old male presents with asymmetric visual field defects, optic atrophy, and facial sensory deficits and has a tumor attached to the dura mater. What is the most likely diagnosis?
Meningioma.
330
❍ A 45-year-old male is in the ICU after sustaining blunt head trauma. He suddenly begins to produce an excessive volume of urine, is markedly thirsty, and has an increase in his plasma osmolality. What is the most likely diagnosis?
DI.
332
❍ What hormones are synthesized and secreted by the adrenal cortex?
Cortisol, aldosterone, adrenal androgens, and estrogen.
333
❍ What hormones are synthesized and secreted by the adrenal medulla?
Epinephrine, norepinephrine, enkephalins, neuropeptide Y, and corticotropin-releasing hormone.
335
❍ What is the pathophysiology of Cushing’s syndrome?
Adrenal corticosteroid hypersecretion.
336
❍ What is the most likely diagnosis of a patient who presents with palpitations, headaches, emesis, a pounding pulse, and retinitis?
Pheochromocytoma.
338
❍ What is the embryologic origin of the adrenal cortex?
Coelomic mesothelial cells.
339
❍ What is the embryologic origin of the adrenal medulla?
Ectodermal neural crest cells.
340
❍ What is the diagnostic algorithm for adrenal cysts?
First evaluate functional status with serum electrolytes, cortisol levels, and urine metanephrines. If functional then resect. If nonfunctional then CT-guided aspiration with cytological analysis is indicated. Indications for resection of nonfunctional cysts are bloody aspirate and abnormal cytology.
342
❍ What is the primary neurotransmitter of sympathetic postganglionic fibers?
Norepinephrine.
344
❍ What are the glands of Zuckerland?
Ectopic adrenal medullary cells located lateral to the aorta, near the origin of the inferior mesenteric artery.
345
❍ What is the arterial supply to the adrenal glands?
The superior suprarenal artery, inferior suprarenal artery, and a branch from the inferior phrenic artery.
347
❍ What is the innervation of the adrenal medulla?
Preganglionic sympathetic neurons from the celiac and renal plexuses via splanchnic nerves.
349
❍ What is the drainage of the right adrenal vein?
The posterior inferior vena cava.
350
❍ Most circulating plasma cortisol is bound to what protein?
Cortisol-binding globulin (CBG), although small amounts are bound to albumin and other plasma proteins.
352
❍ What conditions cause low levels of plasma CBG?
Liver disease, multiple myeloma, obesity, and the nephrotic syndrome.
354
❍ What is the effect of glucocorticoids on insulin and glucagon?
It stimulates production of glucagon and inhibits secretion of insulin.
356
❍ What are the physiologic actions of aldosterone?
Reabsorption of sodium and excretion of potassium, hydrogen, and ammonia from the renal tubules. It also stimulates active sodium and potassium transport in epithelial tissues (i.e., sweat glands, gastrointestinal mucosa, and salivary glands).
358
❍ What is the most common cause of Cushing’s syndrome?
A pituitary microadenoma.
359
❍ What tumor most commonly causes ectopic ACTH secretion?
Small cell carcinoma of the lung.
360
❍ What is the expected result of the dexamethasone suppression test in a patient with an ectopic source of ACTH secretion?
Dexamethasone should fail to suppress cortisol secretion.
362
❍ Where are the sex steroids produced?
In the zona reticulosis of the adrenal cortex.
364
❍ What is the initial evaluation of a patient suspected of having Cushing’s syndrome?
A urinary-free cortisol level (markedly elevated) and a low-dose dexamethasone suppression test (no suppression of cortisol).
366
What is the most likely diagnosis of a patient with elevated free cortisol levels, an elevated plasma ACTH, and persistent elevation of free cortisol after low- and high-dose dexamethasone administration?
An ectopic source of ACTH.
369
❍ What tests are useful in differentiating hypercortisolism caused by pituitary sources of ACTH from those caused by ectopic sources of ACTH?
The dexamethasone suppression test and the metyrapone test.
371
❍ What is the most common cause of primary hyperaldosteronism?
A solitary adrenal adenoma.
372
❍ What enzymatic deficiency is associated with most cases of the adrenogenital syndrome (congenital adrenal hyperplasia)?
21-Hydroxylase.
374
❍ What are the characteristics of Nelson’s syndrome?
Marked hyperpigmentation of the skin and visual disturbances.
376
❍ What is the most common cause of acute adrenocortical insufficiency?
Withdrawal of chronic steroid therapy.
377
❍ What is the most common cause of spontaneous adrenal insufficiency?
Autoimmune destruction of the adrenal glands (greater than 80%).
378
❍ What is the most commonly associated disorder in patients with autoimmune adrenocortical insufficiency?
Hashimoto’s thyroiditis.
379
❍ What is Waterhouse–Freiderichsen syndrome?
Acute adrenal hemorrhage secondary to sepsis (classically meningococcal).
381
❍ What is the most useful test to evaluate a patient suspected of having adrenocortical insufficiency?
The rapid ACTH stimulation test.
382
❍ What is the treatment for patients with acute adrenocortical insufficiency?
Intravenous hydrocortisone (100 mg every 6 hours for 24 hours), correction of volume depletion, dehydration, hypotension, hypoglycemia, and correction of precipitating factors.
385
❍ What is the test of choice to distinguish hyperplasia from an adenoma as the cause of primary hyperaldosteronism?
Measurement of plasma aldosterone concentration after change in posture. Only patients with an adenoma experience a postural decrease in aldosterone.
388
❍ What are the classic clinical manifestations of primary hyperaldosteronism?
Hypertension with spontaneous hypokalemia.
390
❍ What is the treatment of choice for patients with a functional aldosteronoma?
Adrenalectomy.
391
❍ What is the treatment of choice for patients with idiopathic hyperaldosteronism (adrenal hyperplasia)?
Medical management with spironolactone, a competitive antagonist of aldosterone (200–400 mg/d in divided doses).
393
❍ At what size should a nonfunctional incidentally identified adrenal mass be resected?
5 cm.
394
❍ What are the serum abnormalities seen with a functional cortisone-secreting adrenal adenoma?
High 24-hour urine cortisol; low ACTH level.
395
❍ Are ACTH levels suppressed by dexamethasone when there is an ectopic (lung CA) source for the ACTH?
No.
397
❍ What stimuli cause adrenal secretion of catecholamines?
Hypoxemia, hypoglycemia, changes in temperature, pain, shock, CNS injury, local wound factors, endotoxin, and severe respiratory acidosis.
400
❍ T/F: Malignant pheochromocytomas are more common in men.
False. They are three times more common in females.
401
❍ What is the diagnostic test of choice to confirm the clinical suspicion of a pheochromocytoma?
Urine metanephrines.
402
❍ Under what conditions should a patient who is undergoing resection of a pheochromocytoma be given preoperative alpha-blockers?
If the systemic blood pressure is greater than 200/130, if they have frequent and severe uncontrolled hypertensive attacks, or if there is a pronounced decrease in plasma volume.
404
❍ What is the incidence of neuroblastoma in children?
Neuroblastoma represents 7% of all childhood cancers. It is the third most common malignancy in childhood (behind brain tumors and hematopoietic-reticular endothelial cell malignancies).
407
❍ What is the most common location of a neuroblastoma?
Intra-abdominal or retroperitoneal (60%–70%).
409
❍ What is a Stage III neuroblastoma?
One that extends in continuity beyond the midline with bilateral lymph node involvement.
411
❍ Complete cures with surgical resection can be obtained for neuroblastomas of what stage(s)?
Stages I, II, and IV-S.
412
❍ What is the treatment of choice for a Stage III neuroblastoma?
Radiation and chemotherapy followed by delayed resection.
413
❍ What are the classic electrolyte findings of hyperaldosteronism?
Hypernatremia and hypokalemia.
414
❍ What syndromes are associated with pheochromocytomas?
MEN 2a, MEN 2b, von Recklinghausen’s disease, tuberous sclerosis, and Sturge–Weber disease.
416
❍ What hormones are secreted by the posterior pituitary?
Oxytocin and vasopressin.
417
❍ What is the action of oxytocin?
It stimulates uterine contraction during labor and elicits milk ejection by myoepithelial cells of the mammary ducts.
420
❍ What are the anatomic and histologic features of pancreatic neuroendocrine tumors?
The only hypervascular pancreatic neoplasms on angiography. This applies to liver metastasis when present as well. Immunohistochemistry defines functionality.
423
❍ What is the clinical picture of insulinoma?
Fasting glucose <45 and relief of symptoms with glucose. High N and C terminus of insulin in blood (exogenous insulin with C terminus only). Insulinoma is the most common islet cell tumor and is benign in 90% of cases.
425
❍ What is the optimal mechanism to localize an insulinoma intraoperatively?
Intraoperative ultrasound.
426
❍ Characterize gastrinomas.
High malignant potential and the most frequent islet cell tumor in MEN syndrome. Localization techniques include endoscopic ultrasound, MRI, and somatostatin-labeled scintigraphy. High serum gastrin levels and severe peptic ulcer disease are characteristic. Most are located in the gastrinoma triangle between the common bile duct/cystic duct junction, third portion of the duodenum, and gallbladder.
429
❍ What is the order of sympathetic blocking medication administration preoperatively for pheochromocytoma?
Alpha blockade preoperatively (phenoxybenzamine) with PRN periop B-blockade as a secondary measure.
431
❍ What is the best predictor of pheochromocytoma malignancy?
Tumor size (10% malignant).
432
❍ What is the localizing study for pheochromocytoma?
MIBG scan. Other modalities include MRI with bright mass on T2-weighted imaging.
