MLT GlobeChemistry: Endocrinology – page 7
123 Chemistry MCQs on Endocrinology with answers and explanations.
PTH samples are best collected into EDTA because:
Answer: A. PTH is more stable in EDTA plasma than in serum
Intact PTH is degraded by proteases, and it is more stable in EDTA plasma, especially if separation is delayed. Samples should be processed promptly.
ID MG-CHE-0141 · Found a mistake? Report it
A patient has mild hypercalcemia with high-normal PTH. The calcium/creatinine clearance ratio is 0.005. The most likely diagnosis is:
Answer: A. Familial hypocalciuric hypercalcemia
A calcium/creatinine clearance ratio below 0.01 suggests FHH, caused by calcium-sensing receptor mutations. Primary hyperparathyroidism usually gives a ratio above 0.02.
ID MG-CHE-0401 · Found a mistake? Report it
A patient has high free T4 and free T3 with a normal TSH (not suppressed). Assay interference has been excluded. The most likely cause is:
Answer: C. TSH-secreting pituitary adenoma
High thyroid hormones should suppress TSH. An inappropriately normal or high TSH suggests a TSH-secreting adenoma or thyroid hormone resistance. Graves disease and T4 overdose suppress TSH.
ID MG-CHE-0406 · Found a mistake? Report it
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