3.2.2. Main Hormones


Estrogen is a sexual hormone produced in the ovaries. Its function is the development and regulation of the female reproductive system and secondary sex characteristics.

Estrogens are responsible for:

  • Hair and nail growth.
  • Distribution of body fat.
  • Breast growth.
  • Nipple development and pigmentation.
  • Size of pelvis.

This hormone is also known to initiate activation processes of the nervous system. In this way they bring physical, psychological, and sexual vitality to women, as well as dynamism and optimism.


Progesterone is a sexual hormone produced in the ovaries, mainly by the corpus luteum. It acts mainly during the second part of the menstrual cycle, the luteal phase. If the embryo is conceived, the uterus and the breasts must be conditioned so that the implantation and development of the embryo occurs in a safe way. Some functions of the progesterone is to keep the endometrium in place, establish the placenta, stimulate the growth of maternal breast tissue, prevent lactation, and strengthen the pelvic wall muscles in preparation for labor. But, if the egg is not fertilized, the corpus luteum breaks down, and the production of progesterone decreases. Therefore  the endometrium is no longer maintained by progesterone, causing itto break down, and menstrual bleeding occurs.  

Progesterone in other scenarios

  • Progesterone is the hormone found in oral contraceptive pills. Either alone or in combination with estrogen, its role is to prevent ovulation, making it nearly 100% effective in preventing pregnancy.
  • Progesterone can also be used as a hormone replacement therapy to relieve symptoms of the menopause in women.

When progesterone levels are too low

  • Irregular and heavy menstrual bleeding can occur.
  • A pregnancy can result in a miscarriage and early labor.
  • It could mean the ovary has failed to release an egg during ovulation, as it happens in women with polycystic ovary syndrome.


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