Introduction Decrease in effective testosterone levels as result of decreased free concentration often as result of decreased production (Leydig and pituitary dysfunction) also result of increased synthesis of SHBG decreased activity at receptor often as result of androgen receptor deficiency May be primary or secondary primary hypogonadism / hypergonadotropic hypogonadism ↓ function of Leydig cells login to view 3 more bullets loss of negative feedback of testosterone results in ↑ LH FSH levels are variable based on presence of inhibin login to view 4 more bullets etiologies include login to view 2 more bullets secondary hypogonadism / hypogonadotropic hypogonadism ↓ function of hypothalamus/pituitary results in ↓ LH and FSH synthesis and consequent ↓ testosterone synthesis etiologies include login to view 2 more bullets Presentation Symptoms ↓ secondary male characteristics osteoporosis result of dysregulated osteoclast activity (normally ↓ by testosterone) infertility ↓ sperm count impotence Treatment Testosterone administration Formulations Topical Intramuscular Subcutaneous Contraindications Prostate cancer Breast cancer