The most likely cause of this patient's false-positive results using the urinary luteinizing hormone (LH) kit is polycystic ovary syndrome (PCOS). Women with PCOS typically have elevated resting LH levels, which may be mistaken on home urinary LH kits for ovulation. The primary clinical manifestations of PCOS are menstrual irregularity (oligomenorrhea or amenorrhea), ovulatory dysfunction with resultant infertility, insulin resistance, and hyperandrogenism. Oligo-ovulation or anovulation can result in endometrial hyperplasia and/or infertility. Hyperandrogenism presents as hirsutism, acne, or androgenic alopecia. Most patients with PCOS also have insulin resistance, and studies have shown an increased incidence of metabolic syndrome, obesity, impaired glucose tolerance, and frank type 2 diabetes mellitus. PCOS remains a diagnosis of exclusion that is made both clinically and with ancillary testing. A patient with PCOS with a positive urinary LH measurement result may interpret this as a true LH surge and expect ovulation to be imminent. Attempts at conception with intercourse or insemination may be focused on this reading and may therefore be ineffective. A more accurate assessment of LH surge and anticipated ovulation in patients with PCOS would be through transvaginal identification of ovarian folliculogenesis and confirmatory serum assessment of reproductive hormones.

Late-onset (nonclassic) congenital adrenal hyperplasia, although a common cause of hirsutism and oligo-ovulation, is typically associated with normal or low LH levels owing to the negative feedback of elevated androgens of adrenal origin on the anterior pituitary.

Functional hypothalamic amenorrhea affects 3% of women between the ages of 18 and 40 years and is a diagnosis of exclusion. Risk factors for this condition include a low body weight and fat percentage, rapid and substantial weight loss, eating disorders, excessive exercise, severe emotional stress, severe nutritional deficiencies, and chronic or acute illness. FSH and LH levels are inappropriately low or normal and cannot account for a positive urinary LH test.

Hypothyroidism and elevated serum prolactin levels suppress rather than elevate serum LH levels and would not account for this patient's increased urinary LH measurement.