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.
Women who take high doses of estrogen should receive a progesterone dose of 300 mg per day. If the dose is 300 mg daily, 200 mg should be taken at bedtime and 100 mg should be taken 2 hours after breakfast for the last 12 to 14 days of estrogen treatment per cycle.