Gigantomastia
Gigantomastia is extreme growth of the breasts,  i.e. 10 pounds per breast and more. Gigantomastia was first described in literature in 1648.  The condition is caused by over-sensitivity to the female hormones estrogen and progesterone, and/or an unusually high quantity of these hormones. Gigantomastia by definition means bilateral benign progressive breast enlargement to a degree that requires breast reduction surgery to remove more than 4 lb of tissue on each side. In severe cases it is possible for women to have breasts that weigh well in excess of 20 lb each. The largest recorded weight was 67 lb per breast.
Gigantomastia can occur as a rare complication of pregnancy, that occurs in 1 out of every 28,000 to 100,000 pregnancies. But it more frequently occurs as juvenile gigantomastia, more known as virginal breast hypertrophy. In spite of the much higher frequency of gigantomastia during the adolescent breast development it is often already surgically reduced before the age of 15 to 17, so that the frequency and magnitude virtually never get to the general public.
There is currently no medical treatment for the condition other than breast reduction surgery. Usually plastic surgery is not approved for this unless there is a weight of at least 3.5 lb per breast and/or at least 1 lb of tissue per breast needs to be removed. But originally such sizes are seen medical normally only in question of aesthetics, because it still is less than the weakened form of gigantomastia: macromastia (5 to 10 lb per breast). And also in cases of macromastia, from the medical point of view, most of the surgeries are unnecessary, but they are carried out nevertheless, because in our society particularly the younger women with bigger breast sizes are afflicted of prejudices.
However, also gigantomastia with breast weights of much more than 10 lb per breast, on healthy bodies it must still not cause any problems, but an excessive size and weight of the breasts can associated with other problems negatively influence osseous illnesses or skin illnesses and can strengthen their consequences and other medical problems.
Lots of women are ashamed of their big breasts and try to hide them, so mostly a wrong body posture and the wrong bra and/or the wrong bra size are the cause of most problems. Without understanding for special attention for a trouble-free living with extreme breast dimensions, it is common for women to complain of headaches, neck pain, upper and lower back pain, and numbness or tingling in the fingers. Because of the weight of the breasts, too narrow bra straps can cause indentation or grooving in the shoulders when wearing the wrong bra size. That can leave permanent scars from chronic irritation. Severe rashes beneath the breasts are common, particularly during periods of warm weather.
With virginal breast hypertrophy, breast growth is sometimes not constant, but rather comes in growth spurts. At times, women may have minimal or no breast growth and then experience a growth spurt where the breasts grow very rapidly in a short time interval. These growth spurts cause great physical discomfort, the main symptoms being red, itchy skin and sometimes a general ache in the breasts. This type of gigantomastia at puberty is rapid and massive. It was first described in 1670. The initial patient died four months after the onset of enlargement. One breast removed after death weighed 64 lb.
Alternatively, especially in puberty, the breasts can grow continuously and absolutely evenly over several years. Such extended, steady growth can result in overdevelopment of normal, healthy breasts to a gigantic extent.

# Sources
- Swelstad MR, Swelstad BB, Rao VK, Gutowski KA. Management of gestational gigantomastia. Plast Reconstr Surg. 2006 Sep 15;118(4):840-8. Review. PMID 16980844
- Baker SB, Burkey BA, Thornton P, LaRossa D. Juvenile gigantomastia: presentation of four cases and review of the literature. Ann Plast Surg. 2001 May;46(5):517-25; discussion 525-6. PMID 11352426
- Juan, Stephen (2007-01-13). "Is it true that a woman's breasts can grow enormously overnight?". The Register. Retrieved 2007-01-22..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"\"""\"""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{display:none;font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}