A 2-year-old boy is evaluated for pubic hair development and penile enlargement that started at age 1. There is a family history of early puberty in his paternal grandfather. Laboratory tests reveal a pubertal testosterone level but a prepubertal Luteinizing Hormone (LH) level that does not increase after a Gonadotropin-releasing hormone (GnRH) agonist stimulation test. What is the most likely genetic cause of this patient’s condition?