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Question 487
Endocrinology → General
Classification
Question
SSBAQuestion Header
A physiological study examines hypothalamic control of anterior pituitary secretion. Which characteristic most accurately determines the effect of hypothalamic releasing-hormone pulsatility?
Question Stem
Select the single best answer.
Options
A
Frequency of releasing-hormone pulses
B
Amplitude of each releasing-hormone pulse
C
Total duration of each releasing-hormone pulse
D
Peak peripheral concentration of the target-gland hormone
E
Degree of plasma protein binding of the releasing hormone
Explanation
Hypothalamic releasing hormones are secreted in pulses, and their physiological effect is determined principally by pulse frequency rather than pulse amplitude. The releasing hormones controlling anterior pituitary function reach the pituitary through vessels in the pituitary stalk.
Option Validity
B) Pulse amplitude is not the principal determinant; frequency is the key variable described for hypothalamic releasing hormones.
C) Pulse duration is not identified as the principal determinant of releasing-hormone effect.
D) Peripheral target-gland hormone concentration participates in endocrine feedback but does not define the hypothalamic pulse characteristic in question.
E) Plasma protein binding is not the determinant of hypothalamic releasing-hormone pulsatility described here.
Further Reading
Saxena, MRCOG-1 Basic Sciences, Endocrinology: Hypothalamus, p. 302.