Male Hypogonadism By Irvin H Hirsch, MD, Sidney Kimmel Medical College of Thomas Jefferson University Reviewed / Revised Feb 2023 View Patient Education Etiology Symptoms and Signs Diagnosis Treatment Key Points Topic Resources Laboratory evaluation of... Causes of Hypogonadism * Hypogonadism is defined as testosterone deficiency with associated symptoms or signs, deficiency of spermatozoa production, or both.