A 19-year-old female with missed menses and weight gain has a negative serum beta-hCG. What is the most appropriate next step in her management?

In this scenario, the 19-year-old female has missed her menstrual periods and experienced weight gain, yet has a negative serum beta-hCG test. Given these symptoms and the negative pregnancy test, it’s crucial to explore other potential underlying causes for her amenorrhea and weight gain.

Testing for thyroid-stimulating hormone (TSH) and prolactin levels is a sensible next step in this case. Both thyroid dysfunction and elevated prolactin (which can indicate issues such as prolactinoma or primary hypothyroidism) can lead to missed periods and significant changes in weight. A proper assessment of these hormone levels can help identify or rule out these conditions, guiding further treatment or management.

Other options like re-testing for pregnancy or checking for follicle-stimulating hormone (FSH) might not directly address the most likely hormonal causes associated with her symptoms, particularly when a clear pregnancy has been ruled out. Therefore, measuring TSH and prolactin is the most appropriate next step to investigate the possible causes of her amenorrhea and weight gain.