What physical manifestations may appear and how soon?
In a young man with KS, the testicles may not develop normally and therefore the levels of the male hormone, testosterone, will not rise at the onset of puberty as they do in normal young men. This will mean that they will not show the increase in muscle development, and the increase in body hair, normally seen at around the age of 12 or 13 years. The voice will tend not to break, and the young man will generally look less masculine. However, it is quite common for many young men to undergo a normal delay in puberty, as this can vary from between the ages of 12 and 18. The difference in men with KS is that in KS their bones will continue to grow, rather than in constitutional delay where the young man will remain quite short until he eventually goes into puberty. The man with KS will therefore appear to be going into puberty as his growth progresses, but the other features may be absent. The normal rise in testosterone during puberty is required to fuse the bones and stop growth, which
