Final answer:
The patient's symptoms suggest endocrine disorders and measuring the serum cortisol level is the next best step for diagnosis, likely indicating Cushing's syndrome.
Step-by-step explanation:
The next best step for diagnosis in this case would be to perform a serum cortisol level test. The symptoms described by the patient, such as weight gain, increased facial hair, and hypertension, along with the negative pregnancy test, are indicative of a disorder called Cushing's syndrome. This syndrome is characterized by the overproduction of cortisol, a hormone produced by the endocrine system. A serum cortisol level test can help confirm the diagnosis by measuring the cortisol levels in the blood.
The symptoms described by the 37-year-old female patient are indicative of an endocrine disorder, with signs that closely resemble two conditions in particular: polycystic ovary syndrome (PCOS) and Cushing's syndrome. While symptoms such as irregular periods, weight gain, acne, and excess facial hair can point towards PCOS, the additional signs of hypertension, truncal obesity, and pink striae alongside a negative pregnancy test suggest a high possibility of Cushing's syndrome. Given these symptoms, the next best step for diagnosis would be to measure the serum cortisol level, which would help in diagnosing or ruling out Cushing's syndrome due to the overproduction of cortisol.