USMLE Step 1 Question 381

Question:

Which of the following is the most likely mechanism of the therapeutic effect of Bromocriptine in female patients with hyperprolactinemia to help increase fertility?

Correct Answer: E.  Dopamine receptor agonist to decrease prolactin release from the pituitary gland

The correct mechanism of action is dopamine receptor agonist to decrease prolactin release from the pituitary gland. In women with hyperprolactinemia, this therapautic effect of decreasing prolactin secretion helps increase fertility. High levels of prolactin inhibit GnRH release and result in secondary ammenorrhea.

Another way to remember the mechanism of action is to remember that dopamine is also known as Prolactin Inhibiting Factor. Thus, a Dopamine Agonist would act like Prolactin Inhibiting Factor and stop Prolactin release from the pituitary gland.

Bromocriptine is not a dopamine receptor antagonist.

A drug that acts as an antiestrogen to decrease feedback inhibition of estrogen on the pituitary gland and hypothalamus is clomiphene. The result of this drug’s mechanism is to increase the release of FSH and LH to enhance ovulation.

Human menopausal gonadotropins and human chorionic gonadotropins act like FSH and LH to induce ovulation without a functioning pituitary.

GnRH preparations administered in a pulsatile manner induce FSH and LH release by acting on the pituitary gland and thus increasing fertility.