Repeated USMLE Questions Step 1- 381

Q- In a case of methemoglobinemia, which one of the following is the most likely cause of the brown color of the patient’s blood?

A- Carbon monoxide

B- Decreased oxygen affinity

C- Oxidized hemoglobin

D- Reduced hemoglobin

C- Oxidized hemoglobin- The brown color is due the oxidation of the iron in the hemoglobin to ferric state (methemoglobin).

Q- Which of the following agents most likely causes vasoconstriction?

A- Bradykinin

B- Histamine

C- Nitric oxide

D- Norepinephrine

D- Norepinephrine- This is the only one on the list can cause vasoconstriction. The others cause vasodilation.

Q- Paraneoplastic hypercalcemia is most likely caused by tumor cells secreting which one of the following substances?

A- Calcitonin

B- Calcitonin-related peptide

C- Parathyroid hormone

D- Parathyroid hormone-related peptide

D- Parathyroid hormone-related peptide- The tumors associated with this condition include squamous cell carcinoma of the lung, endometrial carcinoma and transitional carcinoma of the urinary bladder. PTHrP is recognized by the receptors for PTH which leads to hypercalcemia.

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