Effects of Testosterone Replacement Therapy (TRT)

The primary effects of Klinefelter’s Syndrome (KS) are low testosterone and infertility. If testosterone levels are below the normal range, testosterone replacement therapy (TRT) is typically prescribed.

Testosterone replacement will not improve fertility. In fact some urologists state that if fertility procedures are being considered then testosterone replacement therapy should be delayed.

Possible positive effects of TRT

TRT can have a very positive effects, although the extent of these will vary from person to person. The most common are:

  • increased assertiveness
  • improved self esteem
  • clarification of thought processes
  • growth of facial and body hair
  • possible reduction in danger of osteoporosis
  • possible improvement in muscle bulk
  • increased  stamina


Possible negative effects of TRT
  • some adults dislike the masculinising effect testosterone will have on their personality and body
  • untreated KS adults have a reduced risk of prostate cancer compared to XY men. TRT  will remove this advantage.  The prostate should be checked before treatment is started and should be monitored
  • Testosterone is known to increase the red blood cell count. This can be a problem if testosterone levels are not monitored
  • increased aggression particularly soon after injections when levels are high
  • mood swings when levels are high or low
  • increased probability of male pattern baldness
  • acne

Next… Fertility Options