Estrogen is produced mainly by the ovaries. It encourages the uterus to start building up a thick lining in preparation for a pregnancy. Estrogen builds up during the egg-maturation phase. When it reaches its peak, it stimulates another pituitary hormone, luteinizing hormone. The egg moves down the fallopian tube towards the uterus.
Progesterone is produced after ovulation by cells in the now empty egg follicle.
If the egg is not fertilized and there is to be no pregnancy, the level of progesterone subsides causing the uterus to shed its lining. But some women s hormones are easily thrown off balance by changes in bodyweight or diet, excitement, stress or illness. And it may cause problems like irregular or missed periods. They usually occur during the two weeks prior to a period and may include bloatedness, breast soreness and swelling, fatigue and irritability. Most women are somewhat aware of the constant internal murmur of their hormones.