In secondary amenorrhea, which is the most common cause?

• A. Polycystic ovary syndrome
• B. Hypothyroidism
• C. Prolactinoma
• D. Pregnancy

Answer: (D)

Pregnancy is the most common cause of secondary amenorrhea. In a woman who previously had menses, stopping for several cycles is most often due to being pregnant. The pregnancy state raises hCG, which supports the corpus luteum and maintains high progesterone (and estrogen) levels, preserving the endometrium and preventing shedding. This hormonal environment suppresses the usual ovulatory cycle, so menses do not occur.

In practice, the first step in evaluating secondary amenorrhea is a pregnancy test. If negative, other causes such as ovarian dysfunction (like PCOS), thyroid disease, or prolactin-related issues are considered. Still, none are as common as pregnancy in most reproductive-age individuals.