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Difficulty: MediumReproductive Endocrinology and Infertility

Match each clinical and laboratory presentation of secondary amenorrhea to the most likely underlying etiology.

  • 26-year-old female marathon runner with amenorrhea. Labs: Low FSH, low LH, low estradiol.Functional hypothalamic amenorrhea
  • 32-year-old female with amenorrhea, vaginal dryness, and hot flashes. Labs: Elevated FSH, low estradiol.Primary ovarian insufficiency
  • 29-year-old female with irregular menses, acne, and a BMI of 32. Labs: Elevated LH to FSH ratio, elevated testosterone.Polycystic ovary syndrome
  • 24-year-old female with amenorrhea and bilateral clear nipple discharge. Labs: Low FSH, low estradiol, elevated prolactin.Pituitary microadenoma

Answer

The presentations map to their respective localizations of the hypothalamic-pituitary-ovarian axis defects based on gonadotropin and estrogen levels.
Secondary amenorrhea evaluation relies on the localization of the physiologic defect. Hypothalamic defects (such as functional hypothalamic amenorrhea) and pituitary defects (such as a prolactinoma) present with low or inappropriately normal FSH and LH levels, known as hypogonadotropic hypogonadism. Ovarian defects (such as primary ovarian insufficiency) present with elevated FSH and LH, known as hypergonadotropic hypogonadism. Polycystic ovary syndrome classically presents with clinical or biochemical hyperandrogenism and an elevated LH to FSH ratio.

Step-by-Step Solution

1
Analyze the laboratory profile of the 26-year-old marathon runner.
Low gonadotropins and low estradiol indicate a central defect; extreme exercise points to functional hypothalamic amenorrhea.
An extreme energy deficit suppresses the hypothalamic-pituitary-ovarian axis to conserve energy.
2
Evaluate the 32-year-old with hot flashes and elevated FSH.
Elevated FSH and low estradiol indicate a primary ovarian defect, which in a woman under 40 represents primary ovarian insufficiency.
Ovarian failure removes the negative feedback on the pituitary, causing FSH levels to rise significantly.
3
Assess the 29-year-old with acne and elevated LH/testosterone.
Clinical and biochemical hyperandrogenism with oligo-ovulation confirms polycystic ovary syndrome.
Increased LH pulsatility drives ovarian theca cells to overproduce androgens.
4
Examine the 24-year-old with galactorrhea and elevated prolactin.
Hyperprolactinemia, likely from a pituitary microadenoma, suppresses GnRH leading to hypogonadotropic hypogonadism.
Prolactin negatively regulates hypothalamic GnRH release, stopping the menstrual cycle.

Key Concept

The underlying pathophysiology of secondary amenorrhea can be differentiated by localizing the defect in the hypothalamic-pituitary-ovarian axis using serum FSH, LH, estradiol, and prolactin levels.
Estimated Time:2m 0s
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Topics

Reproductive Endocrinology and Infertility

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