The phenomenon of “bidirectional regulation” in traditional Chinese medicine (TCM), as one of its characteristic therapeutic effects, embodies the treatment principle of “achieving equilibrium as the therapeutic goal”. However, the underlying dynamic mechanism governing the selection of regulatory direction cannot be adequately explained through the static “component-target” paradigm of modern pharmacology or the empirical induction of traditional “pattern-effect” relationships. To address this theoretical bottleneck, this study, grounded in the intrinsic logic of TCM thinking, introduces and elaborates on the theoretical concept of “dynamic tendency”, constructing a dynamic explanatory framework that organically integrates “body state”, “medicinal properties”, and “effect direction”. This study proposes the basic approach of “discerning the dynamic tendency to clarify the mechanism, and following the dynamic tendency to regulate accordingly”. It innovatively defines three core categories—“disease tendency”, “tendency towards homeostasis”, and “herbal tendency” and, based on the principle of “guiding according to the tendency”, constructs a ternary dynamic response model of “disease tendency-tendency towards homeostasis-herbal tendency”. This model redefines the essence of bidirectional regulation in TCM as follows: within the context of a specific “disease tendency”, the body's inherent self-balancing trend—the “homeostatic tendency” is activated yet lacks the conditions to restore equilibrium. The “herbal tendency”, as an exogenous intervention with a consistent directional property, precisely coordinates with and stimulates this “homeostatic tendency”, thereby guiding the system back to dynamic balance from various states of deviation. Furthermore, the paper analyzes the bidirectional regulatory mechanisms of single herbs (such as Dahuang-Cijili), herb pairs (such as Chaihu-Huangqin), and compound formulas (such as Guizhi Tang) through the lens of the “disease tendency-homeostatic tendency-herbal tendency” framework. Extending the “tendency” theory to the level of clinical diagnosis and treatment, this study aims to provide a new perspective and theoretical foundation for deepening TCM clinical thinking from “pattern differentiation” toward “tendency differentiation and mechanism discernment”, and from “formula selection” toward “precise tendency alignment”. This is intended to promote the modern interpretation and development of “tendency-based” theory in TCM.

potential  /  guiding according to the tendency  /  bidirectional regulation  /  homeostasis  /  traditional Chinese medicine theory  /  regulatory system