The female body is a complex system, and hormones play a major role in regulating its functions. Estrogen and progesterone are the two main sex hormones in women, and they are produced mainly in the ovaries, adrenal glands, and placenta. Estrogen is responsible for sexual and reproductive development, while progesterone helps to stabilize menstrual cycles and prepare the body for pregnancy. Testosterone is also present in lower amounts in women, and it can affect sexual desire.
Hormonal imbalances can cause changes in libido and other health problems. At puberty, the pituitary gland begins to produce large amounts of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which stimulate the production of estrogen and progesterone. During a period, blood and tissue from the uterus leave the body through the vagina. Estrogen and progesterone levels are very low at this time, and this can lead to irritability and mood swings. The pituitary gland also releases FSH and LH, which increase estrogen levels and indicate the growth of follicles in the ovaries. As the dominant follicle continues to grow, it will produce more estrogen.
This increase in estrogen stimulates the release of endorphins that increase energy levels and improve mood. Estrogen also enriches the endometrium, which is the lining of the uterus, in preparation for a possible pregnancy. During the ovulatory phase, levels of estrogen and LH in the body peak, causing a follicle to burst and release its egg from the ovary. The ruptured follicle releases progesterone, which thickens the lining of the uterus and prepares it to receive a fertilized egg. Once the egg reaches the end of the fallopian tube, it attaches to the uterine wall.
An unfertilized egg will cause estrogen and progesterone levels to drop. This marks the beginning of the premenstrual week. Progesterone levels rise steadily during the first few weeks of pregnancy, causing the cervix to thicken and form a mucous plug. The increase in hCG levels in the body then stimulates greater production of estrogen and progesterone. This rapid increase in hormones causes symptoms in the early stages of pregnancy, such as nausea, vomiting, and increased need to urinate. Hormone levels drop when a pregnancy ends and gradually return to pre-pregnancy levels.
When a person breastfeeds, it can lower estrogen levels in the body, which can prevent ovulation from occurring. A person reaches menopause when a full year has gone by without having a menstrual period. After menopause, the ovaries will only produce very small but constant amounts of estrogen and progesterone. Estrogen, progesterone, and testosterone all affect sexual desire and arousal. Having higher levels of estrogen in the body promotes vaginal lubrication and increases sexual desire.
Increases in progesterone may reduce sexual desire. There is some debate about how testosterone levels affect female sexual desire; low testosterone levels may reduce sexual desire in some women. However, testosterone therapy seems ineffective in treating low sexual desire in women. Sex hormones affect neurotransmitters and shape the adult female brain during periods of hormonal transition. If a woman has too much estrogen compared to other sex hormones such as testosterone, she may experience low sexual desire along with other negative effects. Many of the hormonal fluctuations that occur throughout a woman's life (puberty, pregnancy, menopause) can cause a decrease in sexual desire.
Along with hormone therapy, optimal hormone balance is achieved with changes in diet, routine exercise, and strategies to reduce stress. Female hormone therapy may slightly increase a woman's risk of uterine (endometrial) cancer, blood clots, and stroke; however these results should be interpreted with caution as Sherwin (199) did not administer a placebo during weeks without hormones.
