Rehmannia glutinosa, commonly used in Traditional Chinese Medicine (TCM), has a long-standing reputation for supporting the body's hormonal system, particularly in the context of balancing the endocrine system, supporting adrenal function, and influencing reproductive hormones. In TCM, Rehmannia is considered a key tonic herb for nourishing the "kidney" system, which is believed to be fundamental to hormonal balance, sexual vitality, and aging. Classical TCM texts and centuries of empirical use cite Rehmannia root as beneficial for conditions associated with hormonal deficiency or imbalance, such as menstrual irregularities, menopausal symptoms, and fatigue.

Scientifically, however, evidence is limited and mostly preliminary. Some animal studies suggest that Rehmannia extracts may influence the hypothalamic-pituitary-adrenal (HPA) axis, modulate corticosteroid levels, or have mild estrogenic effects, but robust clinical trials in humans are lacking. Most modern uses for supporting the "hormones" or endocrine system are therefore primarily justified by tradition and historical use patterns in East Asian herbalism rather than strong scientific validation. Consequently, while there is a basis for its use within herbal traditions, evidence from well-designed human studies is insufficient, and more research is needed to confirm its efficacy for hormonal support.