Thieme Test Prep for the USMLE®: Learning Pharmacology through Clinical Cases (eBook)

Mario Babbini, Sandeep Bansal (Autoren)

eBook Download: EPUB

2018 | 1. Auflage
Georg Thieme Verlag KG
978-1-63853-433-4 (ISBN)

Infos

<p><em>Learning Pharmacology through Clinical Cases</em> by Mario Babbini and Sandeep Bansal uniquely integrates the preclinical disciplines, which is crucial for pharmacological problem solving and learning to think critically. Each case portrays a real-life scenario, promoting a bridge from foundational knowledge to its application. A series of USMLE-style questions with thorough explanations guide the reader through a comprehensive understanding of relevant basic science disciplines such as physiology, pathology, and microbiology, followed by a detailed analysis of the pharmacology.</p><p><strong>Key Features</strong></p><ul><li>Nearly 50 case studies mirror situations seen in every-day practice</li><li>In-depth coverage of drugs in the context of specific disease states and clinical situations</li><li>Comprehensive cases encompass medical/family/drug history, physical examination, lab findings, diagnosis, pharmacotherapy, and follow-up</li><li>One set of multiple choice questions addresses related basic science content. A second set covers topics related to the pharmacology, such as mechanism of action, adverse effects, and contraindications.</li></ul><p>This essential, highly practical resource will help medical students build problem-solving skills, assess pharmacology knowledge, and fully prepare for board examinations.</p>

Textauszug

Case 1

Acromegaly

G.A., a 40-year-old man, complained to his physician of difficulty seeing objects in the periphery, excessive sweating, and gradual enlargement of his hands and feet. His shoe size had increased by two sizes in the last 2 years, and his wedding ring also had to be resized. He had recently started snoring, and he would waken in the morning with a headache. His facial skin had also become oilier.

Physical examination showed a man with a slightly protruding lower jaw. His vital signs were as follows: blood pressure 130/88 mm Hg, pulse 80 bpm, respirations 22/min.

The patient’s skin was thickened, and excessive perspiration was noted on his hands and feet. Visual field examination revealed temporal hemianopia. Dental examination showed increased dental spacing.

Pertinent laboratory results on admission were as follows:

Blood hematology

Blood glucose, fasting: 130 mg/dL (normal, 70–110)

Growth hormone (GH) suppression test: GH 20 ng/mL (normal, < 2)

Insulin-like growth factor 1 (IGF-1) 890 ng/mL (normal, 138–410)

Prolactin: 50 ng/mL (normal, < 20)

Free testosterone: 2.5 pg/mL (normal for age 40, 6.8–21.5)

Luteinizing hormone (LH): 2.2 U/L (normal 6–23)

Follicle-stimulating hormone (FSH): 1.3 U/L (normal 4–25)

MRI scan of the head

Pituitary macroadenoma encroaching on the optic chiasma.

Colonoscopy

Normal, with no evidence of tumor growth.

The diagnosis was acromegaly due to GH-secreting adenoma. G.A. was scheduled for transsphenoidal resection of the adenoma.

Six weeks postsurgery, G.A. felt much better, and his peripheral vision had also improved. However, a lab exam showed that his GH and IGF-1 levels were still high due to the extrasellar invasion of the adenoma. He was thus started on therapy with a somatostatin analogue and a dopamine agonist.

Questions

1. G.A. was diagnosed with a growth hormone–secreting adenoma. Which of the following types of cells constitute a major part of this adenoma?

A. Basophilic cells

B. Acidophilic cells

C. Chromophobe cells

D. Null cells

2. G.A. was found to have increased fasting glucose levels. Which of the following was most likely the cause of this finding?

A. Suppression of glucagon secretion

B. Increased glycogenesis

C. Antagonism of insulin action

D. Decreased excretion of glucose in urine

E. Increased cortisol levels

3. G.A. was found to have decreased blood levels of testosterone. Which of the following was most likely the cause of this decrease?

A. GH-induced inhibition of Leydig cell function

B. Prolactin-induced increase of gonadotropin release

C. Increased somatostatin release

D. GH-induced impairment of Sertoli cell function

4. G.A. felt well after surgical resection of his adenoma. However, because of the residual tumor, his GH and IGF-1 levels were still high. He started a therapy with a somatostatin analogue. Which of the following drugs was most likely prescribed?

A. Octreotide

B. Lansoprazole

C. Somatropin

D. Sunitinib

E. Leuprolide

5. Which of the following signal transduction pathways best describes the molecular mechanism of octreotide action to suppress somatotroph function?

A. Stimulation of adenylyl cyclase

B. Closure of potassium channels

C. Activation of mitogen-activated protein kinase

D. Inhibition of adenylyl cyclase

E. Opening of calcium channels

6. G.A. was prescribed a dopamine agonist. Which of the following drugs was most likely administered?

A. Bromocriptine

B. Cabergoline

C. Olanzapine

D. Sumatriptan

E. Buspirone

7. Nausea is a common adverse effect of dopamine agonists. Which of the following brain structures is most likely the primary site of the action that mediates this adverse effect?

A. Frontal cortex

B. Amygdala

C. Area postrema

D. Paraventricular nucleus

E. Vestibular nuclei

8. Which of the following could most likely develop as an adverse effect of octreotide early in the course of treatment of acromegaly?

A. Kyphosis

B. Cholelithiasis

C. Hyperprolactinemia

D. Esophageal varices

E. Abdominal pain

9. G.A. did not respond adequately to the octreotide and cabergoline therapy. He was subsequently prescribed pegvisomant. Which of the following phrases best describes the mechanism of action of pegvisomant?

A. Inhibition of growth hormone release

B. Blockade of somatostatin receptors

C. Activation of insulin-like growth factor 1 receptors

D. Activation of growth hormone receptor

E. Blockade of growth hormone receptors

10. Which of the following signs and symptoms of acromegaly are unlikely to resolve with drugs that reduce growth hormone release or its action?

A. Soft tissue changes

B. Prognathism

C. Hyperglycemia

D. Oiliness of skin

E. Hyperhidrosis

Answers and Explanations

Learning objective: Describe the histology of the anterior pituitary gland.

1. Answer: B

The cells of the anterior pituitary gland are classified as acidophils or basophils, depending on their affinity for acidic or basic histology dyes, respectively. Acidophilic cells look red and basophilic cells look blue under the microscope. The five types of anterior pituitary cells can be subdivided as follows:

Somatotrophs (GH-secreting cells): acidophilic

Lactotrophs (prolactin-secreting cells): acidophilic

Corticotrophs (adrenocorticotropic hormone [ACTH]-secreting cells): basophilic

Gonadotrophs (FSH- and LH-secreting cells): basophilic

Thyrotrophs (thyroid-stimulating hormone [TSH]-secreting cells): basophilic

A See correct answer explanation.

C Chromophobe cells are cells that stain poorly with histology dyes and look pale under the microscope.

D Null cells are lymphocytes that lack characteristic surface markers that are found on B and T lymphocytes. They are not the hormone-secreting cells of the anterior pituitary.

Learning objective: Describe the effects of growth hormone on glucose metabolism.

2. Answer: C

Growth hormone antagonizes the function of insulin, resulting in decreased peripheral utilization of glucose and increased gluconeogenesis. Normally, GH release peaks during sleep, and, in concert with other hormones, such as cortisol, helps to maintain glucose levels within the normal range to provide a continuous supply of glucose to the vital organs. However, in cases of GH-secreting adenoma, GH levels are constantly high, which results in increased blood glucose levels that could lead to diabetes mellitus. G.A.’s fasting glucose levels were above the normal range of 70 to 110 mg/dL, indicating the antagonizing effects of GH on insulin activity.

A Glucagon secretion is not suppressed by growth hormone. Moreover, suppression of glucagon secretion would not cause increased blood glucose levels.

B Glycogenesis is decreased, not increased, due to antagonism of insulin actions.

D Glucose is normally filtered by the glomerulus and is completely reabsorbed by the renal tubules. When blood glucose is > 200 mg/dL, it exceeds the renal reabsorption capacity, and glucose starts appearing in the urine. Decreased renal excretion of glucose cannot occur in the presence of high blood glucose.

E Increased cortisol levels could cause hyperglycemia, but cortisol levels are not increased by GH-secreting adenoma. Actually, the anterior pituitary adenoma could compress the surrounding corticotroph cells and impair corticotropin release to decrease cortisol synthesis in the adrenal cortex.

Learning objective: Describe the likely causes of decreased gonadal function in a patient with a pituitary mass.

3. Answer: A

A pituitary tumor mass, especially a macroadenoma (functional or nonfunctional) can press against other cell types in the anterior pituitary to impact their function. In case of a nonfunctional pituitary adenoma, usually the first cells impacted are GH-secreting cells, and then in sequential order, gonadotrophs, thyrotrophs, and corticotrophs are impacted. G.A. had a...

Produkt-Details

• Erscheint lt. Verlag: 10.1.2018
• Sprache: englisch
• Themenwelt: Medizin / Pharmazie ► Gesundheitsfachberufe
• Themenwelt: Medizin / Pharmazie ► Medizinische Fachgebiete ► Pharmakologie / Pharmakotherapie
• Themenwelt: Medizin / Pharmazie ► Studium
• Schlagworte: Babbini • pharmacology • USMLE
• ISBN-10: 1-63853-433-0 / 1638534330
• ISBN-13: 978-1-63853-433-4 / 9781638534334