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Question 503
Endocrinology → General
Classification
Question
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Two patients undergo assessment of tendon reflexes. One has untreated thyrotoxicosis and the other has established hypothyroidism. Which paired finding best distinguishes the expected reflex physiology?
Question Stem
Select the single best answer.
Options
A
Shortened reflex duration in thyrotoxicosis and prolonged reflex relaxation in hypothyroidism
B
Prolonged reflex relaxation in both disorders
C
Absent tendon reflexes in thyrotoxicosis and shortened reflex duration in hypothyroidism
D
Shortened reflex duration in both disorders
E
No characteristic alteration in tendon reflexes in either disorder
Explanation
Hyperthyroidism reduces tendon reflex duration, whereas hypothyroidism produces prolonged tendon reflexes, classically a hung-up ankle jerk. The contrast reflects the opposing physiological effects of excess and deficient thyroid hormone.
Option Validity
B) Prolonged reflex relaxation is characteristic of hypothyroidism, not thyrotoxicosis.
C) Thyrotoxicosis is associated with shortened reflex duration, while hypothyroidism prolongs reflex relaxation.
D) Reflex duration is prolonged rather than shortened in hypothyroidism.
E) Characteristic and contrasting tendon-reflex abnormalities are described in both conditions.
Further Reading
Saxena, MRCOG-1 Basic Sciences, Endocrinology: Hyperthyroidism and Hypothyroidism, p. 309.