Which of the following is a Prolactin-inhibiting hormone?

MP NHM CHO-2024 (Shift-2)

Applied Physiology

Easy

Appeared in: MP NHM CHO-2024 (Shift-2)

Explanation

Dopamine is the primary physiological inhibitor of prolactin secretion from the anterior pituitary gland.
It is released by neurons in the arcuate nucleus of the hypothalamus and travels through the portal blood vessels to the pituitary.
Dopamine acts on D2 receptors on the lactotroph cells of the anterior pituitary, suppressing the synthesis and release of prolactin.
This inhibitory control is tonic, meaning it is constantly active unless interrupted by specific stimuli like suckling.

Option B: Adrenaline (epinephrine) is a catecholamine released by the adrenal medulla, primarily involved in the acute stress ('fight-or-flight') response. It does not have a primary role in inhibiting prolactin.
Option C: Noradrenaline (norepinephrine) is a neurotransmitter and hormone central to the sympathetic nervous system's response to stress. It is not the primary inhibitor of prolactin.
Option D: Corticotropin-Releasing Hormone (CRH) is a hypothalamic hormone that stimulates the anterior pituitary to release Adrenocorticotropic Hormone (ACTH), which in turn stimulates cortisol release from the adrenal glands. It does not inhibit prolactin.

Visual 1: Diagram - A diagram of the hypothalamic-pituitary axis. This visual should clearly show the arcuate nucleus of the hypothalamus releasing dopamine, which travels down the portal system to the anterior pituitary and has an inhibitory effect on lactotroph cells, thus blocking prolactin release.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal regulation of prolactin secretion as background academic context rather than a clinical decision trigger.
Understanding that dopamine inhibits prolactin is crucial for managing hyperprolactinemia (abnormally high prolactin levels), which can cause infertility, menstrual irregularities, and galactorrhea (inappropriate milk production).
Conditions of hyperprolactinemia are often treated with dopamine agonists like bromocriptine and cabergoline, which mimic dopamine's inhibitory action.
Nurses must be aware that many antipsychotic medications work by blocking dopamine receptors. A common side effect is hyperprolactinemia, and the nurse should monitor for signs like galactorrhea or amenorrhea.

How to Approach the Question

First, identify the core of the question, which is to find the 'Prolactin-inhibiting hormone'.
This is a factual recall question from the topic of endocrinology.
Recall the functions of the hormones listed in the options. Think about the hypothalamic-pituitary axis.
Remember that prolactin regulation is unique because it is primarily under inhibitory control, unlike other pituitary hormones like TSH or ACTH which are under stimulatory control.
Associate the term 'Prolactin-Inhibiting Hormone' (PIH) with its chemical name, Dopamine.
Eliminate the other options by identifying their primary roles: Adrenaline and Noradrenaline are for the 'fight-or-flight' response, and CRH stimulates ACTH release.

Concept Tested & Keywords

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