Question

question 13

how does synthetic progesterone in contraceptives prevent pregnancy?

• it prevents implantation of the fertilized egg.
• it prevents the lh surge and thus prevents ovulation.
• it constricts the cervix to prevent the sperm from reaching the egg.
• it binds to the fertilized egg and destroys it.

Explanation:

Analyze the physiological effect of progesterone on the hypothalamic-pituitary-ovarian axis

$$ \text{Synthetic progesterone} \implies \text{Negative feedback on hypothalamus/pituitary} \implies \downarrow \text{GnRH, } \downarrow \text{LH/FSH} $$

Determine the primary mechanism of preventing ovulation

$$ \text{Suppression of LH surge} \implies \text{Prevention of ovulation} $$

Evaluate the given multiple-choice options

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Answer:

• It prevents implantation of the fertilized egg.
• It prevents the LH surge and thus prevents ovulation. (Correct answer)
• It constricts the cervix to prevent the sperm from reaching the egg.
• It binds to the fertilized egg and destroys it.