The mechanism of action of the herbs is not known precisely, and undoubtedly varies according to the type of infertility problem being treated and the herb formula that is used. The traditional Chinese views are that infertility tends to arise from one or more of three prominent causes:1. A “deficiency” syndrome prevents the hormonal system from properly influencing the sexual and reproductive functions. This is said to be a weakness of the “kidney and liver” which may influence various body functions producing symptoms such as frequent urination, weakness and aching of the back and legs, impotence, irregular menstruation, and difficulties with regulation of body temperature. Deficiency syndromes are treated with tonic herbs that are said to nourish qi (e.g., ginseng, codonopsis, atractylodes, astragalus), blood (e.g., tang-kuei, peony, ho-shou-wu, gelatin), yin (e.g., lycium fruit, ligustrum, eclipta, ophiopogon), or yang (e.g., epimedium, cistanche, cuscuta, eucommia), and are selected according to the overall evaluation of symptoms.2. A “stagnancy” syndrome prevents the sexual and reproductive organs from functioning despite normal hormone levels and normal ability to respond to hormones. This is said to involve a stagnancy of “qi and blood,” which has the impact of restricting circulation to the tissues involved. Qi stagnation is often noted by tense muscles, restrained anger, and digestive disorders; herbs for resolving the stagnancy include bupleurum, cyperus, lindera, and various citrus products. Other symptoms that might arise include abdominal pain or bloating, chronic inflammation, and formation of lumps (including cysts and tumors). Blood stagnation often occurs following childbirth, surgery, injury, or severe infection and is typically noted when there is severe pain (such as dysmenorrhea), or hard swellings and obstructions; abnormal cell growth, including dysplasia and cancer, are thought to involve blood stagnation. Herbs such as salvia, red peony, persica, and carthamus may be used.3. A “heat” syndrome, which causes the affected organs to function abnormally. Heat syndromes may be associated with an infection or inflammatory process. This type of syndrome can produce abnormal semen quality leading to male infertility, while gynecologic infections can maintain female infertility by blocking the passages, altering the mucous membrane conditions, or influencing the local temperature. Herbs that inhibit infections and reduce inflammation are used, including gardenia, phellodendron, patrinia, and lonicera.In each case, the purpose of the Chinese herbs is to rectify the underlying imbalance to restore normal functions. Western medicine can diagnose tubal blockage (which usually corresponds to blood stagnancy in Chinese medicine) and infection (which corresponds to heat syndromes of Chinese medicine) and in many cases can successfully treat these causes of infertility. However, Western medicine often fails to diagnose deficiency syndromes and most of the stagnancy syndromes. Therefore, the majority of Chinese herb formulas to be applied in the U.S. are those that counteract the deficiency (called tonics) and those that resolve the stagnancy (called regulators). A description of Chinese herb formulas used for infertility is presented in the appendix to Chinese Herbology, a training manual produced by the Institute for Traditional Medicine.The hormonal effects of Chinese herbs used to treat impotence and infertility and to prevent miscarriage have been demonstrated in laboratory experiments. For example, the laboratory evaluation of Huanjing Decoction (composed of rehmannia, ho-shou-wu, ligustrum, morus fruit, achyranthes, dipsacus, cynomorium, astragalus seed, and cuscuta) was administered to senile mice for four months, two weeks treatment, one week break. Estradiol and dihydrotestosterone receptors in the nucleus of thymic cells were decreased to levels found in young mice; cytosol estradiol receptors increased. Also, the formula influenced the immune system: it increased thymus weight, thymic index, and prevented atrophic changes in the ultrastructures of thymic lymphocytes and epithelial reticular cells.