Estradiol is the most common form of a type of hormone known as estrogen. This hormone is present in both men and women but has most of its function in women. Estradiol helps drive the menstrual cycle and is also involved in bone strength and in puberty. Estradiol is primarily produced by the ovaries and the adrenal gland. Low levels of estradiol can be due to genetic factors (such as Turner's Syndrome), or due to the shutting down of the ovaries (either as a result of menopause or as a result of premature ovarian failure).
Estradiol is a critical hormone for the menstrual cycle. Low levels of estradiol cause irregularities in the menstrual cycle. In the case of menopause, estradiol levels plummet dramatically, leading to a cessation of menstrual periods. Less extreme estradiol deficiencies results in irregular periods (periods that do not occur every month) or abnormally light periods. Low estradiol levels in adolescents can lead to delayed puberty, resulting in menstrual periods not beginning until later in life. Adolescent women with delayed puberty will also develop secondary sex characteristics, such as the development of breasts and pubic hair, later in life.
Low estradiol can also cause sexual symptoms. These side effects can include a loss of interest in sex (lowered sex drive) and increased dryness of the vagina. This can lead to pain during sexual intercourse and possible irritation and damage to the vagina.
Estradiol is required for the proper balance of bone breakdown and reformation, a process known as bone remodeling. Low estradiol causes the amount of bone matrix that is being broken down to outpace the new bone being built, leading to weakened bones. Osteoporosis can result in multiple stress fractures in the ribs and vertebrae, as well as easy breakage of larger bones, such as the femur.
Sudden drops in estradiol can also cause symptoms as the body adjusts to lower levels of the hormone. This can lead to hot flashes, fatigue, increased sweating (especially at night), headache and problems sleeping. The lower estradiol levels can also cause mood swings, thinning of the hair and increased abdominal fat.