Final answer:
The most likely diagnosis for the patient is Androgen Insensitivity Syndrome (AIS), where despite having a male genetic makeup, the individual has resistance to male hormones and may present with female physical traits.
Step-by-step explanation:
The likely diagnosis for a 16-year-old patient with primary amenorrhea, high serum testosterone, high luteinizing hormone (LH), normal follicle-stimulating hormone (FSH), and a palpable bulge in the left groin is Androgen Insensitivity Syndrome (AIS). This condition occurs when a person who is genetically male (having one X and one Y chromosome) is resistant to male hormones (androgens). As a result, the person has some or all of the physical traits of a woman, but the genetic makeup of a man.
While Polycystic Ovary Syndrome (PCOS) also presents with high levels of androgens, the presence of a groin bulge possibly indicates a testicular tissue that has not descended, which is more consistent with AIS. In AIS, individuals often have normal or elevated LH due to the body's inability to respond to androgens, leading to lack of negative feedback and continuous stimulation of LH secretion. As opposed to PCOS, where LH and FSH may be elevated due to a different pathophysiology involving insulin resistance and anovulation. The distinction is critical because the management and treatment implications differ greatly between the two conditions.