Hypogonadism occurs when the gonads produce little or no sex hormones. There are two types: primary, where the problem is in the gonads, and secondary, where the issue is in the brain. Causes include genetic disorders, infections, tumors, and injuries. Symptoms vary between males and females but include impaired sexual development and function. Hormone tests and imaging exams diagnose and identify the cause of low hormone levels. Treatment replaces missing sex hormones through medications, supplements, or hormone therapy tailored to the individual.