Hypogonadism is a medical term for a defect of the reproductive system which results in lack of function of the gonads (ovaries or testes). The gonads have two functions: to produce hormones (testosterone, estradiol, antimullerian hormone, progesterone, inhibin B), activin and to produce gametes (eggs or sperm). Deficiency of sex hormones can result in defective primary or secondary sexual development, or withdrawal effects (e.g., premature menopause) in adults. ...

the state of being a eunuch (either because of lacking testicles or because they failed to develop)

Hypogonadism as related to Male hypogonadism