93. The popular birth control pills for women have a combination of synthetic forms of estradiol
and progesterone. Which one of the following statements is INCORRECT with regard to their
function as contraceptive?
(A) The pills inhibit the release of GnRH leading to inhibition of gonadotropin-stimulated ovarian
function
(B) They act directly on the pituitary gland to inhibit gonadotropin surges
(C) The low dose of estradiol in the pill inhibits the release of FSH, and thus blocks ovulation
(D) The synthetic forms of estradiol and progesterone bring about their effects by binding to their
respective intracellular receptors

Combined oral contraceptive pills, containing synthetic estradiol and progesterone, primarily prevent pregnancy by suppressing ovulation through hormonal feedback. The incorrect statement among the options highlights a misunderstanding of their pituitary interaction.

Correct Answer

Option (B) is incorrect: Birth control pills do not act directly on the pituitary gland to inhibit gonadotropin surges.

Option Breakdown

(A) GnRH Inhibition

Pills inhibit GnRH release from the hypothalamus via progestogen negative feedback, reducing gonadotropin pulse frequency and blocking FSH/LH secretion for ovarian suppression.

(B) Direct Pituitary Action (Incorrect)

These contraceptives mimic natural feedback to decrease hypothalamic GnRH pulses, indirectly affecting the pituitary; no direct pituitary targeting occurs for gonadotropin surges.

(C) FSH and Ovulation Block

Low-dose estradiol provides negative feedback to the pituitary, suppressing FSH and preventing follicular development, which blocks ovulation.

(D) Receptor Binding

Synthetic estradiol and progesterone bind intracellular receptors, altering gene expression to produce contraceptive effects like ovulation inhibition.