Good health depends on balance between testosterone and estrogen in both males and females. Neither hormone is just “male” or “female”. The goal of this article was to study the effect of the aromatase enzyme in human testes, the effects of high and low hormone levels on the testes, as well as the location of aromatase in testes. This information would aid in learning more about the cause of testicular disease.
Aromatase enzyme stimulates the conversion of testosterone and androstenedione into estrogens. The gene for aromatase is expressed in many tissues (including testis), and hormone production controls male fertility. Exposure to environmental estrogens can cause male infertility and disorders of the reproductive system, such as hypospadias (small testes), cryptorchidism (undescended testes), and testicular cancer.
In sexually active male animals, estrogen production is in the Leydig cell of the testes. Aromatase may control motility of sperm cells, and sperm cells are thought to control local estrogen levels. Excess estrogen reduces sperm quality, as in Bisphenol A (an endocrine disruptor) exposure. Aromatase enzyme is necessary for normal testicular function.
In healthy aging men, testosterone levels decline and estradiol levels increase, possibly due to increasing aromatase activity in aging. People with Klinefelter’s syndrome (KS) have four times normal aromatase activity and can develop low testosterone levels and high estradiol levels. Estrogen is a potent proliferative agent and can lead to cancer of the female breast and male testes.
Aromatase has been studied regarding the effects of excess and deficiency by testing mouse models of these states. An interruption of estrogen can interfere with the production of sperm, and fertility declines when the mice have high estrogen levels or low androgen levels. The latter mice had Leydig cell adenomas, but did not have malignant tumors. In humans, aromatase is necessary for normal testicular size and sperm counts.
Men with aromatase deficiency due to mutation are very rare. They have normal or high testosterone levels and undetectable estrogen levels. Their sperm development is abnormal, and they are unable to have children.
Rarely, men can have aromatase excess. They have increased levels of estrogen. They may have pre-pubertal gynecomastia (breast enlargement). They may have increased tumor rates, especially of the testes, and the tumors of the testes commonly become calcified and can be seen on X-ray.
CONCLUSION: A great deal of research has been done on the value of aromatase in male fertility. Estrogens appear to be very important to normal testes and male fertility. (Further research is being done.)
NOTES: DHEA (dehydroepiandrosterone) and androstenedione are precursors of testosterone, and are available in health food stores.
Aromatase inhibitors are used to treat certain breast cancers. There are natural aromatase inhibitors, such as flavonoids and an herb named kudzu (Pueraria lobata.)
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