The Chinese medical concept of Kidney Jing could roughly be translated as the inherited reproductive essence that in women encompasses the function of the ovaries, including the formation of the ova, as well as some aspect of the pituitary function. Jing in men affects their physical vitality as well as the quality and quantity of sperm they produce. When Kidney Jing is strong a child will develop well in the womb and will in turn inherit their parent's vitality. Weakness of Kidney Jing will affect a man or woman's ability to produce children of their own and the formation of the sexual organs during puberty may be impaired. It may also affect the onset of puberty, sexual drive and physical growth. When Jing is plentiful this increases fertility and longevity. It has for instance been noted that women who successfully conceive in their 40s often live longer than average.
Jing deficiency in women manifests as an abnormal absence of menstruation, resistant ovary syndrome or sporadic and intermittent cycles, or premature menopause. As has been noted, in men it results in lower sperm counts, and less mobile or impaired development of the sperm. Although a person's Jing is primarily determined in the womb by the health of their parents (termed Pre-Heaven Jing) it can also be strongly affected in life by diet and exercise (termed Post-Heaven Jing). This situation has been recognised in China for centuries and has resulted in the development of complex dietary therapy and Chi Gung exercises to address this situation.