Polycystic Ovary Syndrome (PCOS): Although the patient denies any hirsutism, the presence of regular menstruation with sometimes heavy flow, an elevated LH level (21.4), and an LH/FSH ratio greater than 2 (considering FSH is 7.8), along with an elevated testosterone level (total 50), are suggestive of PCOS. The patient's BMI of 26, which falls into the overweight category, and an insulin level of 9.4, also support this diagnosis, as insulin resistance is a common feature in many PCOS patients.

Thyroid Dysfunction: Abnormal thyroid function can affect menstrual regularity and fertility. Although not directly indicated by the provided lab values, thyroid-stimulating hormone (TSH) levels should be checked to rule out hypothyroidism or hyperthyroidism, as these conditions can influence menstrual patterns and hormone levels.
Hyperprolactinemia: Elevated prolactin levels can disrupt menstrual cycles. Although not provided, a prolactin level should be checked, especially if other symptoms such as galactorrhea or headaches are present.
Idiopathic Hyperandrogenism: This condition involves elevated androgen levels without the other diagnostic features of PCOS. Given the patient's elevated testosterone and regular menstruation, this could be considered if PCOS criteria are not fully met.

Androgen-Secreting Tumors: Although rare, these tumors can cause significant hyperandrogenism. The patient's denial of hirsutism and the presence of regular menstruation make this less likely, but it should not be missed due to its potential impact on health.
Cushing's Syndrome: This condition, caused by excess cortisol, can lead to hyperandrogenism, irregular menstruation, and weight gain. The patient's BMI and insulin level might suggest metabolic syndrome, which can be associated with Cushing's Syndrome, making it a diagnosis not to miss.
Congenital Adrenal Hyperplasia (CAH): A group of inherited disorders that affect the adrenal glands, leading to hyperandrogenism. Late-onset CAH could present with irregular menstruation and hyperandrogenism, although the regular menstruation in this patient makes it less likely.

Hyperandrogenism due to Other Rare Conditions: Such as glucocorticoid resistance or other genetic disorders affecting steroidogenesis. These conditions are rare and typically present with more severe symptoms or additional findings beyond those described in the patient.
Pituitary or Adrenal Disorders: Other than those mentioned, such as pituitary adenomas not secreting prolactin or rare adrenal tumors, could potentially cause the patient's symptoms but are less likely given the information provided.