I do not understsnd your question, however, you should be aware of the role estrogens play in sprrmatogrnesis. Sertoli cells have Estrogen receptors and in eels E2 is required for the renewal of spermatogonia.
Dr. Al-salhie. Testosterone is one of the hormones that is formed in the pathway of steroidogenesis both in males and females and is converted to estradiol by aromatase enzyme in both ovarian follicles in females and seminiferous tubules of testes in males. The synthesis mechanism involves signaling from LH and FSH on theca cells and granulosa cells, respectively, in ovaries, and leydig cells and sertoli cells, respectively, in testes. The mechanism is called two-cell two-hormone hypothesis. In fact, progesterone, another important reproductive hormone, is the precursor of testosterone in the steroid pathway. Different species have diverse pathways of testosterone synthesis and then from that the estradiol synthesis, depending upon the delta 4 or delta 5 pathway. I hope this answers your question.
Certain target tissues express aromatase, an enzyme which facilitates the conversion of circulating testosterone to estradiol and androstenedione to estrone, thus Dr. Mohd Amin Beg is absolutly right and explained the question thoroughly.
There were nice answers above, but I can just complement that testosterone is converted into estradiol by aromatase (CYP19) in a lot of tissues, including brain, fat, skeletal muscle, gonads, etc.
In addition, testosterone is converted into estrogens during the critical period of sexual differentiration, which plays a very important role in sexual brain organization.
men cannot make estrogens, and therefore must convert testosterone into estrogen. Low testosterone may result in low estrogen levels, but not always. High amounts of the enzyme aromatase, which converts testosterone to estrogen, can deplete testosterone levels while raising estrogen levels dangerously high.
Dr. Sarhat, I am not sure what do you mean by "men cannot make estrogens, and therefore must convert testosterone into estrogen". Is there any other way except testosterone (androgen) pathway to "make" estradiol (estrogens)? I am sorry it might be that I might be misunderstanding your comment, but I must emphasize for sake of any misunderstanding your comment might generate that there is no other way except the indicated pathway for synthesis of estradiol in the animal or human body (male or female).