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Difficulty: MediumReproductive Endocrinology and Infertility

A 21-year-old university student is brought to the outpatient clinic by her older sister because she has not had a menstrual period in 8 months. She experienced menarche at 13 years of age and subsequently had regular 29-day cycles. Over the past year, she has been training intensively for a regional triathlon and adhering to a strict, calorie-restricted vegan diet. She reports feeling occasionally fatigued but denies headaches, visual disturbances, or hot flashes. She takes no medications and is not sexually active. Her temperature is 36.6°C (97.9°F), blood pressure is 96/60 mm Hg, and pulse is 48/min. Her BMI is 16.8 kg/m2. Physical examination shows a very thin woman with fine, soft hair over her arms and back. Pelvic examination is unremarkable, and a urine pregnancy test is negative. Which of the following serum hormone profiles is most likely to be found in this patient?

  1. Decreased follicle-stimulating hormone, decreased luteinizing hormone, decreased estradiolAnswer
  2. B
    Elevated follicle-stimulating hormone, elevated luteinizing hormone, decreased estradiol
  3. C
    Normal follicle-stimulating hormone, elevated luteinizing hormone, elevated testosterone
  4. D
    Normal follicle-stimulating hormone, decreased luteinizing hormone, elevated prolactin
  5. E
    Normal follicle-stimulating hormone, normal luteinizing hormone, normal estradiol

Answer

Decreased follicle-stimulating hormone, decreased luteinizing hormone, decreased estradiol
The correct answer is decreased follicle-stimulating hormone (FSH), decreased luteinizing hormone (LH), and decreased estradiol. This patient's presentation of secondary amenorrhea, intense athletic training, calorie restriction, low BMI, bradycardia, and lanugo hair is classic for functional hypothalamic amenorrhea (FHA). FHA develops due to a relative energy deficit, leading the body to suppress the hypothalamic-pituitary-ovarian (HPO) axis to conserve energy. This suppression decreases the pulsatile secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus. As a result, the anterior pituitary is not adequately stimulated, leading to decreased levels of FSH and LH. Without gonadotropin stimulation, the ovaries do not produce normal amounts of estradiol, creating a state of hypogonadotropic hypogonadism. FHA is a key component of the female athlete triad, which includes low energy availability, menstrual dysfunction, and decreased bone mineral density.

Step-by-Step Solution

1
Identify the most likely cause of the patient's secondary amenorrhea based on history and physical examination.
The patient has Functional Hypothalamic Amenorrhea (FHA).
Her presentation of intense athletic training, strict calorie-restricted dieting, significant bradycardia, low BMI, and lanugo hair strongly suggests severe energy deficiency leading to reproductive suppression.
2
Determine the underlying pathophysiology of Functional Hypothalamic Amenorrhea.
FHA is characterized by the suppression of pulsatile Gonadotropin-Releasing Hormone (GnRH) release from the hypothalamus.
In states of negative energy balance, the body attempts to conserve energy by downregulating non-essential physiological processes, such as the reproductive axis.
3
Correlate the pathophysiology with the expected laboratory profile.
Decreased GnRH leads to decreased production of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which in turn leads to decreased estradiol.
The anterior pituitary requires pulsatile GnRH stimulation to release gonadotropins; without them, the ovaries are not stimulated to produce estrogen, resulting in hypogonadotropic hypogonadism.

Key Concept

Pathophysiology and laboratory findings in functional hypothalamic amenorrhea
Estimated Time:1m 0s
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Topics

Reproductive Endocrinology and Infertility

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