From: david j 8/04/99 20:26:24 Subject: nipples post id: 6061 why do men have nipples?????? From: Karl Kruszelnicki 8/04/99 23:53:01 Subject: re: nipples post id: 6086 The fertilised egg starts up with a single, round, fertilised egg. It then grows, and divides, and grows, and divides. At first, the cells all look identical. Soon, after more divisions, they begin to look different. By 16 weeks (or so) the genital organs begin to look different. Nipples are programmed into both sexes. Nobody really knows why men have nipples. It's difficult to make a human, and it might be easier to leave the program for making nipples running in both sexes. Anyway, sometimes, men can lactate - but usually, only under extraordinary circumstances. Men don't generally lactate, unless they're suffering from some strange disease, or unless they're taking hormones. But starvation can make men lactate. In one Japanese concentration camp alone, there were 500 starved male prisoners-of-war who had significant breast development, and who were lactating. In fact, at the end of World War II, when prisoners-of-war were released from concentration camps, many thousands of cases of men lactating were recorded. It's all to do with hormones. Before puberty, there is no observable difference between the breasts of boys and girls. But at puberty, the hormone estradiol in young girls starts off the process of growth and division in the tubular duct system of the breast, as well as causing changes in the nipples. This does not happen in young boys. But it has been found that breast development, identical to that which happens in girls, can be stimulated in boys, by the administration of the hormones estrogen and progesterone, in a ratio of about one to fifty. So you can "grow" a breast with the right hormones, but to make milk, you need hormones which are made in the brain. The most important of these is prolactin. Now both men and women make the female hormone, oestrogen, and the male hormone, testoserone, and prolactin, but in different amounts. In the body, various hormones are constantly being made by various glands, and these hormones are constantly being broken down, for example, by the liver. So the blood level of any given hormone depends on how much is being made, and how much is being broken down. In these starved men in the concentration camps, their glands had atrophied (or shrunk) a bit, so they were making less hormones. But in these men, the liver had shrunk enormously, so that it was quite unable to break down even the small amounts of various hormones that were released, and it’s thought that this is how come the men grew breasts, and then lactated. This forum is un-moderated. The views and opinions expressed are those of the individual poster and not the ABC. The ABC reserves the right to remove offensive or inappropriate messages.