Human chorionic gonadotrophin (hCG) is a hormone that can be used to treat infertility in men taking testosterone replacement therapy. This hormone works by stimulating the testes to produce testosterone, which helps to improve fertility. In order to use hCG for fertility, the patient must first receive a diagnosis of male hypogonadism from a doctor. Once diagnosed, the doctor may prescribe hCG injections, which will help to stimulate the testes to produce testosterone. In addition, the patient should also receive regular monitoring and medical care to ensure that the testosterone levels remain within a normal range. Additionally, lifestyle changes such as a balanced diet, regular exercise, and stress-relief techniques can also help improve fertility in men taking testosterone replacement therapy. Finally, if all other treatments are unsuccessful, the doctor may suggest assisted reproductive technology such as in vitro fertilization or intracytoplasmic sperm injection to aid in conception.