What is the most appropriate next step in managing a 19-year-old female with secondary amenorrhea and a negative beta-hCG?

The most appropriate next step in managing a 19-year-old female with secondary amenorrhea and a negative beta-hCG is to check thyroid-stimulating hormone (TSH) and prolactin levels. This step is crucial because secondary amenorrhea can be caused by several underlying conditions, including endocrine disorders such as hypothyroidism and hyperprolactinemia.

Hypothyroidism may lead to menstrual irregularities due to its effect on the hypothalamic-pituitary-gonadal (HPG) axis, while elevated prolactin can inhibit the secretion of gonadotropins, further affecting menstrual cycles. By assessing these hormones, a clinician can identify or rule out these common causes of secondary amenorrhea. This targeted approach also allows for timely diagnosis and management of any underlying conditions, which is especially important in a young patient presenting with amenorrhea.

Starting hormonal contraceptives immediately might be appropriate in some scenarios for managing menstrual irregularities, but without first determining the underlying cause, it could mask a potentially significant health issue.

Performing a urine pregnancy test would be unnecessary in this case since the beta-hCG test has already been confirmed as negative.

Scheduling a pelvic ultrasound is often used to investigate structural abnormalities, but