The cysts are of different sizes and multiple cysts can give the breasts a nodular consistency. The problem occurs in 20 to 40 percent of premenopausal women. Any breast lumps should, of course, be brought to the attention of a physician. FBD is thought to be primarily due to an increased estrogen to progesterone ratio, though the hormone prolactin is also higher than normal.
Elevated prolactin is thought to be due to the high estrogen levels.
Other factors are thought to contribute to the problem. Caffeine is one such factor. Those who made no changes in their caffeine consumption failed to improve at all. Another factor is low thyroid hormone levels or lack of iodine. Yet another factor is a low fiber diet and constipation.