SBA — Single Best Answer · Review
Question 488
Endocrinology → General
Classification
Question
SSBAQuestion Header
A woman with primary hypothyroidism develops hyperprolactinaemia. Which regulatory change provides the most direct explanation for the raised prolactin concentration?
Question Stem
Select the single best answer.
Options
A
Reduced secretion of thyrotrophin-releasing hormone
B
Increased secretion of thyrotrophin-releasing hormone
C
Increased hypothalamic dopamine secretion
D
Reduced sensitivity of prolactin secretion to thyrotrophin-releasing hormone
E
Increased gonadotrophin-releasing hormone pulse frequency
Explanation
Primary hypothyroidism is associated with increased thyrotrophin-releasing hormone (TRH), and TRH stimulates prolactin secretion. Prolactin is unusual among anterior pituitary hormones because its hypothalamic control is predominantly inhibitory through dopamine. Hyperprolactinaemia can in turn reduce GnRH pulsatility.
Option Validity
A) Primary hypothyroidism increases rather than reduces TRH drive.
C) Dopamine inhibits prolactin secretion; increased dopamine would oppose hyperprolactinaemia.
D) TRH stimulates prolactin secretion; reduced responsiveness would not explain the rise described.
E) Hyperprolactinaemia reduces GnRH pulsatility rather than being explained by increased GnRH pulse frequency.
Further Reading
Saxena, MRCOG-1 Basic Sciences, Endocrinology: Prolactin, pp. 305–306.