Normally yin and yang in the body maintain a dynamic balance through the interactions of inter-opposition, inter-dependence, inter-restriction and inter-transformation. If such a dynamic balance is impaired by six exogenous abnormal climatic factors, endogenous impairment by abnormal changes of emotions, improper diet or overwork and over-rest, the normal relationships between the viscera, the meridians, qi and blood will be affected, leading to various complicated pathological changes.
The main pathological changes caused by imbalance between yin and yang are predomination and decline of yin and yang, mutual impairment of yin and yang, mutual rejection of yin and yang, mutual transformation of yin and yang as well as loss of yin and yang.
Relative predomination and decline of yin and yang
Relative predomination and decline of yin and yang refer to the changes of yin and yang beyond the normal range due to various factors. Relative predomination and decline of yin and yang directly cause excess syndrome and deficiency syndrome. Relative predomination of yin and yang leads to excess syndrome while relative decline of yin and yang leads to deficiency syndrome. Predomination and decline of yin and yang also decide the nature of disease. Relative predomination of yang and deficiency of yin cause heat syndrome while domination of yin and deficiency of yang bring on cold syndromes.
1. Relative predomination of yin and yang
When yin or yang becomes predominant, it becomes a pathogenic factor and causes excess syndrome because "excess of pathogenic factors leads to excess syndrome". When yin becomes predominant, it will bring on cold syndromes; when yang becomes predominant, it will lead to heat syndromes.
(1) Relative predomination of yang:
Relative predomination of yang refers to excess-heat syndrome marked by predomination of yang and non-deficiency of yin due to relative predomination of yang-qi and hyperactivity of body functions during the course of disease. It results either from imbalance between yin and yang, or from attack of exogenous warm pathogenic factors, or from attack of pathogenic factors of yin nature that transforms into heat with yang, or from endogenous impairment due to abnormal changes of emotions and heat transformed from abnormal changes of emotions, or from heat transformed from qi stagnation, stagnant blood, phlegm and retention of food that make yang-qi predominant. Predomination of yang leads to heat, so usual clinical manifestation is fever, accompanied by profuse sweating, thirst, reddish complexion, reddish tongue with yellowish coating, full and large or rapid pulse; or accompanied by pathogenic heat disturbing the interior with the symptoms of dysphoria, insomnia, mania, dry feces and scanty brownish urine, etc.
Predomination of yang impairs yin. So predomination of yang is usually characterized by consumption of yin-fluid. At the medium and advanced stages of disease, pathogenic yang gradually declines and the consumption of yin-fluid is more and more serious, eventually leading to yin-deficiency syndromes.
(2) Relative predomination of yin:
Relative predomination of yin refers to excess-cold syndrome marked by relative predomination of yin-qi, decline of body functions and retention of pathological substances in the course of disease. It may result either from attack of pathogenic cold and dampness, or from excessive intake of cold and uncooked food that makes yin-qi in the body predominant. Predomination of yin generates cold and obstructs yang-qi, clinically leading to cold symptoms, such as chills, dispiritedness, pale complexion, anhidrosis, preference for hot water, cold limbs, loose stool, clear urine, whitish tongue coating, deep and slow pulse, etc.
Since predomination of yin leads to disorder of yang, relative predomination of yin obstructs or impairs yang. At the medium and advanced stages of disease, pathogenic yin gradually declines and yang-qi becomes more and more deficient, eventually bringing on yang-deficiency syndromes.
2. Relative decline of yin and yang
Normally both yin and yang pertain to healthy qi in the body. Once yin or yang declines, insufficiency of healthy qi will be caused. So both relative decline of yin and yang can lead to deficiency syndrome because "loss of essence causes deficiency". Usually relative decline of yin brings on deficiency-heat syndrome while relative decline of yang results in deficiency-cold syndrome.
(1) Relative decline of yang:
Relative decline of yang results either from imbalance between yin and yang and excessive consumption of yang-qi, or from congenital weakness and insufficiency of fire in life-gate, or from improper postnatal care and impairment of yang-qi, or from impairment of yang-qi during the course of disease. Deficiency of yang-qi generates cold and clinically brings on deficiency-cold syndrome and decline or weakness of viscera functions, leading to the symptoms of aversion to cold, cold limbs, mental lassitude, poor appetite, loose stool, clear and profuse urine, and deep-slow-weak pulse, etc.
Yang-deficiency syndrome mainly involves the spleen and the kidney, mainly characterized by deficiency of kidney-yang. Since kidney-yang is the foundation of yang-qi in the other organs, deficiency of kidney-yang will make spleen-yang insufficient. Since the spleen is the acquired base of life, deficiency of spleen-yang weakens the functions of transportation and transformation, eventually leading to insufficient production of blood and qi and aggravating the state of yang deficiency.
Deficiency of yang makes it difficult to restrict yin, leading to interior exuberance of yin-cold or retention of water-dampness or interior blockage of stagnant blood which may further stagnate qi activity and bring on serious dysfunction of the viscera.
(2) Relative decline of yin:
Relative decline of yin may result either from imbalance between yin and yang and excessive consumption of yin-essence, or from congenital weakness and insufficiency of yin-fluid, or from improper postnatal care and exhaustion of yin-fluid, or from insufficiency of yin-fluid in the course of disease. Deficiency of yin generates heat and clinically brings on deficiency-heat syndrome and various hyperactivities of viscera functions, leading to the symptoms of emaciation, low fever, feverish sensation in the five centers (palms, soles and chest), night sweating, dry mouth, dry feces, scanty urine, reddish tongue coating or no tongue coating, thin and rapid pulse, etc.
Deficiency of yin mainly involves the liver and the kidney, mainly marked by kidney-deficiency. Since kidney-yin is the foundation of yin in the other viscera, deficiency of kidney-yin makes liver-yin insufficient.
Deficiency of yin cannot restrict yang and brings on endogenous heat and fire with the symptoms of irascibility and insomnia, etc. Insufficiency of liver-yin makes liver-yang hyperactive. Hyperactivity of liver-yang transforms into fire that disturbs the upper orifices and leads to dizziness, headache or even apoplexy and syncope, etc.
Inter-consumption of yin and yang
Yin and yang depend on each other and insufficiency of any side will affect the other. Protracted deficiency of yin will affect yang and cause deficiency of yang. Similarly, prolonged deficiency of yang will affect yin and cause deficiency of yin. Such an inter-consumption of yin and yang eventually results in deficiency syndrome of both yin and yang.
1. Deficiency of yin affecting yang
Deficiency of yin affecting yang means that consumption of yin-fluid involves yang-qi and makes yang-qi insufficient in production or exhausted, leading to a morbid state marked mainly by deficiency of yin with the manifestation of deficiency of both yin and yang.
2. Deficiency of yang affecting yin
Deficiency of yang affecting yin means that consumption of yang-qi involves yin-fluid and makes yin-fluid insufficient in production, leading to a morbid state marked mainly by deficiency of yang with the manifestation of deficiency of both yin and yang.
Inter-rejection of yin and yang
Inter-rejection of yin and yang, a special pathogenesis in imbalance between yin and yang, includes two aspects: predomination of yin rejecting yang and predomination of yang rejecting yin. The cause of such a pathological change lies in the fact that either yin or yang becomes predominant and drives the other side outside, leading to a complicated pathological condition marked by disagreement between the nature of disease and symptoms.
1. Predomination of yin rejecting yang
Predomination of yin rejecting yang refers to a pathological state in which predominant yin drives yang-qi outside, leading to a pathological change marked by true interior cold and false exterior heat. The nature of this syndrome is cold, but the manifestations appear febrile because yang-qi is driven outside. Take deficiency of yang generating interior cold for example. If it develops to a stage marked by extreme predomination of yin-cold and external floating of yang, a pathological change of predominant yin rejecting yang will be caused, the manifestations of which include cold limbs, diarrhea with undigested food and indistinct pulse due to predominance of yin-cold as well as some pseudo-febrile signs such as fever in spite of desire for quilt in the body and reddish cheeks.
2. Predomination of yang rejecting yin
Predomination of yang rejecting yin refers to a pathological state in which predominant yang drives yin outside, leading to a cold-like pathological change. Since pathogenic heat has deepened into the body and cannot be dispersed outside, there is pseudo-cold symptoms though the syndrome is febrile in nature. Take exuberant interior heat in febrile disease for example. Since heat is superabundant, yin and yang are in disharmony and yin-qi is blocked and rejected. The manifestations include feverish sensation in the chest, dry mouth, and dry and red tongue as well as cold limbs and aversion to cold due to the fact that extreme change of yang appears like yin.
Inter-transformation of yin and yang
Inter-transformation of yin and yang means that yang-heat syndrome may change into yin-cold syndrome and yin-cold syndrome may turn into yang-heat syndrome in the course of a disease.
1. Transformation of yang into yin
The nature of the disease originally pertains to yang-heat. But when yang-heat develops to a certain degree, it will turn into yin-cold. For example, some febrile diseases show a series of heat symptoms at the early stage, such as high fever, thirst, reddish tongue, yellowish tongue coating and rapid pulse, indicating that the syndrome is obviously of yang-heat. However, improper treatment or extreme exuberance of pathogenic factors may suddenly lead to such critical signs of yin-cold as low body temperature, cold limbs, cold profuse sweating and indistinct pulse. This shows that the nature of the disease has been changed. Such a change is quite different from true-heat and false-cold syndrome in yang syndrome appearing like yin syndrome.
2. Transformation of yin into yang
The nature of the disease originally pertains to yin-cold. But when yin-cold develops to a certain degree, it will turn into yang-heat. For example, attack of exogenous pathogenic cold leads to a series of wind-cold symptoms at the early stage, such as serious aversion to cold and light fever, headache, body pain, thin and whitish tongue coating, and floating-tense pulse, indicating wind-cold affecting the superficies. Eventually it develops into a yang heat syndrome marked by high fever, sweating, thirst, reddish tongue, yellowish tongue coating and rapid pulse. This shows that yin syndrome has been transformed into yang syndrome and cold syndrome has been turned into heat syndrome. Such a change is quite different from true-cold and false-heat syndrome in yin syndrome appearing like yang syndrome.
Loss of yin and yang
Loss of yin and yang refers to a critical pathological state caused by sudden loss of great quantity of yin-fluid or yang-qi. Loss of yin or yang also pertains to relative predomination and relative decline of yin and yang, quite different from relative predomination and decline of yin or yang in the occurrence and severity of disease.
1. Loss of yang
Loss of yang is usually caused by predomination of pathogenic factors and weakness of healthy qi to control pathogenic factors, frequent deficiency of yang and overstrain, wrong application of diaphoresis and profuse sweating that result in sudden loss of yang-qi, leading to the symptoms of profuse sweating, cold sensation in the skin, feet and hands, lying with the knees drawn up, spiritual lassitude and indistinct pulse, etc.
2. Loss of yin
Loss of yin is usually caused by exuberant pathogenic heat, violent vomiting, profuse sweating and diarrhea that result in loss of great quantity of body fluid with the symptoms of emaciation, curled skin, sunken ocular orbit, scanty and sticky sweating, irascibility and very weak pulse, etc.
Though loss of yin and loss of yang may appear solitarily, the loss of one side often leads to immediate exhaustion of the other because yin and yang depend on each other to exist. Thus untimely treatment of loss of yin or loss of yang may lead to death because "separation of yin and yang exhausts essence. "