The second carbon is connected to the amino group. Amino means there is an NH 2 group bonded to the carbon atom. In the image, you see a + and a -. Those positive and negative signs are there because, in amino acids, one hydrogen atom moves to the other end of the molecule. An extra H gives you a positive charge.
Ranges of normal estrogen levels are measured in parts pg/ml of estradiol. In normal reproductive age women, during the menstrual cycle, estradiol levels range from 50-400 pg/ml. The actual normal level of estrogen varies during different parts of the menstrual cycle. In menopause, the general range may be 10-20 pg/ml.
The standard upper reference range for estrogen in men is <54. According to medical science, if you're below 54 pg/mL, you're good to go! I have to disagree! 54 is too high! If you're anywhere near 50 pg/mL, you're approaching the feminization zone, especially if you have low testosterone levels.