SBA — Single Best Answer · Review
Question 506
Endocrinology → General
Classification
Question
SSBAQuestion Header
A lesion compresses the pituitary stalk and interrupts normal hypothalamic influence on the anterior pituitary. Which hormonal abnormality is particularly expected?
Question Stem
Select the single best answer.
Options
A
Reduced prolactin due to loss of hypothalamic stimulation
B
Increased prolactin due to loss of dopaminergic inhibition
C
Reduced prolactin due to increased dopamine delivery
D
Increased prolactin due to increased gonadotrophin secretion
E
Reduced prolactin due to loss of posterior pituitary secretion
Explanation
Prolactin differs from most anterior pituitary hormones because its dominant hypothalamic control is inhibitory. Dopamine inhibits prolactin secretion. Compression of the pituitary stalk reduces this inhibitory influence and can therefore cause hyperprolactinaemia.
Option Validity
A) The dominant hypothalamic influence on prolactin is inhibition by dopamine rather than stimulation.
C) Pituitary stalk compression reduces rather than increases delivery of the inhibitory hypothalamic influence.
D) Gonadotrophin secretion is not responsible for the hyperprolactinaemia caused by pituitary stalk compression.
E) Prolactin is an anterior pituitary hormone and its rise in stalk compression reflects loss of hypothalamic inhibition.
Further Reading
Saxena, MRCOG-1 Basic Sciences, Endocrinology: Prolactin.