A 16-year-old girl is brought to the clinic for evaluation of absent menarche. Her medical history is unremarkable. She is at the 10th percentile for height and 50th percentile for weight. Physical examination reveals absent breast development (Tanner stage I) and normal external female genitalia. Arrange the following diagnostic and therapeutic steps in the most appropriate chronological sequence for the evaluation and management of this patient.
- 1Perform a pelvic ultrasound to evaluate the internal reproductive anatomy
- 2Measure serum follicle-stimulating hormone (FSH) levels
- 3Perform a peripheral blood karyotype analysis
- 4Identify a 45,X chromosomal complement
- 5Initiate low-dose systemic estrogen therapy
Answer
The correct sequence is: Pelvic ultrasound -> Serum FSH measurement -> Karyotype analysis -> Identification of 45,X -> Initiation of estrogen therapy.
The standard evaluation of primary amenorrhea begins with a physical examination and pelvic ultrasound. The ultrasound determines the presence or absence of a uterus, which bifurcates the diagnostic algorithm. Since a uterus is present, the next step is to measure serum FSH to evaluate the hypothalamic-pituitary-ovarian axis. An elevated FSH level indicates primary ovarian insufficiency (hypergonadotropic hypogonadism). The most common cause of this in a 16-year-old is a chromosomal abnormality, necessitating a karyotype. Once Turner syndrome (45,X) is diagnosed definitively, estrogen therapy is initiated to stimulate pubertal development and protect bone density.
Step-by-Step Solution
Key Concept
The evaluation of primary amenorrhea begins with a pelvic ultrasound to confirm the presence of a uterus, followed by FSH measurement to distinguish between central and peripheral causes, and culminates in a karyotype if primary ovarian insufficiency is identified.
Estimated Time:1m 30s