What is the next best step in evaluating an 18-year-old female with primary amenorrhea (absence of menstruation), normal physical examination, and Tanner stage four breast and pubic hair development?

From the Guidelines

The next best step in the evaluation of this patient is to measure serum follicle-stimulating hormone (FSH) levels (option C). This 18-year-old female with primary amenorrhea (never having had a menstrual period) requires hormonal evaluation to determine the underlying cause. FSH is particularly important because it helps distinguish between hypothalamic-pituitary causes versus ovarian causes of amenorrhea, as suggested by the guidelines for evaluating abnormal uterine bleeding associated with ovulatory dysfunction 1. Her normal secondary sexual development (Tanner stage 4 breast and pubic hair development) and normal pelvic examination findings suggest that she has adequate estrogen production and normal reproductive anatomy. Her low body weight relative to height and intensive exercise regimen (marathon training) point toward functional hypothalamic amenorrhea as a likely diagnosis, which would typically show low or normal FSH levels. Measuring FSH would help confirm this suspicion or point toward other etiologies if elevated, such as premature ovarian failure, which is a consideration in the evaluation of infertility and amenorrhea 1. Other tests like karyotype would be more appropriate if there were signs of gonadal dysgenesis, while testosterone would be indicated if virilization were present. Pelvic ultrasound might be considered later but is less informative than hormonal testing as the initial step given her normal pelvic examination.

Some key points to consider in the evaluation of primary amenorrhea include:

• The importance of a thorough medical history and physical examination, including assessment of secondary sexual characteristics and pelvic examination findings 1
• The role of hormonal testing, including FSH, in distinguishing between different causes of amenorrhea
• The consideration of lifestyle factors, such as intense exercise and low body weight, in the diagnosis of functional hypothalamic amenorrhea
• The potential need for further testing, such as pelvic ultrasound or karyotype analysis, depending on the results of initial evaluation.

From the Research

Evaluation of Primary Amenorrhea

The patient presents with primary amenorrhea, defined as the absence of menstrual bleeding by the age of 16 in the presence of normal secondary sexual characteristics, or the absence of menstrual bleeding by the age of 14 if there are no secondary sexual characteristics 2. Given the patient's age, physical development, and lack of menstrual bleeding, further evaluation is necessary to determine the underlying cause.

Initial Assessment

The patient's physical examination reveals normal breast and pubic hair development, indicating normal secondary sexual characteristics. The pelvic examination also reveals a normal-sized uterus and ovaries. These findings suggest that the patient's reproductive organs are developed, but further testing is needed to determine the cause of her amenorrhea.

Next Steps in Evaluation

The next step in the evaluation of this patient would be to assess her hormonal levels, specifically:

• Serum follicle-stimulating hormone (FSH) to determine if she has hypergonadotropic or hypogonadotropic hypogonadism 3
• Serum luteinizing hormone (LH) to evaluate her pituitary function and determine if she has a hormonal imbalance 4
• Other hormone levels, such as estrogen and testosterone, may also be evaluated to determine the underlying cause of her amenorrhea

Diagnostic Tests

Some possible diagnostic tests that may be ordered include:

• Pelvic ultrasound to evaluate the patient's reproductive organs and rule out any anatomical abnormalities
• Karyotype to determine if the patient has any chromosomal abnormalities, such as Turner syndrome
• Hormone level tests, such as FSH, LH, and estrogen, to evaluate the patient's hormonal balance and determine the underlying cause of her amenorrhea

Key Considerations

It is essential to consider the patient's overall health and well-being when evaluating her amenorrhea. A thorough physical examination, medical history, and laboratory tests are necessary to determine the underlying cause of her condition 5, 6.