Human Chorionic Gonadotropin (hCG) is a glycoprotein hormone produced primarily by the placenta during early pregnancy and plays a central regulatory role in the hypothalamic–pituitary–gonadal (HPG) axis, where its structure and function closely resemble luteinizing hormone (LH). Through its interaction with the LH/hCG receptor (LHCGR) on gonadal tissues, hCG stimulates Leydig cells in the testes to produce testosterone, supporting spermatogenesis and maintaining androgen-dependent physiological processes. This LH-mimicking activity has led to the wide investigation and clinical use of hCG in contexts such as male hypogonadism, infertility, and endocrine disorders involving impaired gonadal function. In research and therapeutic settings, hCG has been shown to preserve testicular volume, prevent testicular atrophy during exogenous testosterone administration by maintaining intratesticular testosterone production, and augment endogenous hormone output in individuals with secondary hypogonadism. Additionally, hCG influences ovarian function in females, promoting follicular maturation and ovulation through its potent gonadotropic signaling. Beyond reproductive physiology, studies suggest hCG may exert immunomodulatory, angiogenic, and anti-apoptotic effects, contributing to placental development and fetal tolerance during pregnancy. Its multifaceted endocrine and paracrine actions continue to make hCG a key hormone in reproductive medicine, endocrine research, and investigations involving male fertility preservation and hormonal regulation.