SBA — Single Best Answer · Review
Question 508
Endocrinology → General
Classification
Question
SSBAQuestion Header
An exogenous hypothalamic releasing factor is administered during endocrine testing. In which circumstance would the pituitary response be expected to be smaller?
Question Stem
Select the single best answer.
Options
A
When endogenous releasing-hormone secretion is absent
B
When the median eminence lies outside the blood-brain barrier
C
When endogenous secretion of the corresponding releasing hormone is greater
D
When releasing-hormone pulse amplitude is reduced but frequency is unchanged
E
When posterior pituitary secretion is increased
Explanation
The response to an exogenous hypothalamic releasing factor is inversely related to endogenous secretion of that releasing hormone. Greater endogenous releasing-hormone secretion is therefore associated with a smaller response to an administered releasing factor.
Option Validity
A) With lower or absent endogenous secretion, the inverse relationship would not predict the smaller response described.
B) The anatomical position of the median eminence outside the blood-brain barrier does not account for reduced responsiveness to an exogenous releasing factor.
D) Pulse frequency, rather than pulse amplitude, is the principal determinant of the effect of pulsatile releasing-hormone secretion; this does not explain reduced responsiveness to an exogenous releasing factor.
E) Posterior pituitary secretion does not determine the response to an exogenous hypothalamic releasing factor.
Further Reading
Saxena, MRCOG-1 Basic Sciences, Endocrinology: Hypothalamus.