Edited by: Joe Hing kwok Chu Both males and females produce testosterone.  

Men produce testosterone in the testes and  adrenal glands and women produce testosterone  in ovaries and adrenal glands. 

The average male has 260 to 1,000 nanograms of testosterone per 100 c.c. of blood plasma and the  average woman has 15 to 70 nanograms of  testosterone per 100 c.c. of blood plasma.

The sex drive of men depends on the level of testosterone and the the number of receptors  they have in the body. Men with low testosterone  can still have a normal sex drive if they have larger amount of receptors.

Usually the level of testosterone fluctuates during  the day. In normal healthy men, the peak is around 8 a.m., and the low is around midnight. In men with   shenyangxu condition, the curve of testosterone production can look like an inverted V. 

As people age the sex hormone concentration in  blood plasma changes. In normal men after middle  age, the concentration of plasma female hormone,

estradiol (E₂) tends to rise, while the levels of  plasma male hormone, testosterone (T)  tend to  remain normal or slightly decrease. As men get  older the estradiol starts to remain at steady levels  and testosterone starts to drop.

Dropping of testosterone in men not only causes  loss of libido and impotence but also causes other illnesses.

In 1976, Phillips found that of 15 middle aged  male patients, 7 had a slower growth of beard, 

3 had gynecomastia , and three had decreased  libido before myocardial infarction occurred.  

Four months before myocardiac infarction, 

plasma E₂ rises significantly while levels of T  were normal.

In 1982, researchers at the Shanghai Hypertension Clinic in China found that  E₂ level and  or E₂/T ratio increased respectively in patients with sick sinus syndrome (1981), as well as in those with Type II diabetes (1982), acute myocardial infarction  (1983) and hypertension (1984).  Administration of  kidney tonics and Yin-yang regulating herbal medicines or practice of certain type of qigong overcame various symptoms, and decreased, to various extent, the E₂ levels and E₂/T ratio.

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