At birth some KS boys may show signs of intrauterine hypogonadism such as micropenis or cryptorchism and although anecdotal, testosterone injections may alleviate this problem. Conflicting data regarding the surge in testosterone (mini-puberty) during the first 3 months has been published; demonstrating either low levels of testosterone,high-normal levels of testosterone or low-normal testosterone. If the mini-puberty during the first 3 months is blunted, a window for testosterone treatment has been proposed in order to reestablish normal testosterone levels and unconfirmed reports about such treatment to infants with KS, particularly in the USA, have been circulated for many years. Interestingly, a recent study by Samango-Sprouse et al. did find a better neuro-developmental outcome in KS boys (n = 34) treated with testosterone in infancy (because of micropenis) compared with KS nontreated boys (n = 67), but unfortunately, the treatment was not randomized or blinded, leaving the study with a great potential for selection bias. However, current knowledge does not support systematic treatment with testosterone in infancy except for cases of micropenis. Randomized controlled trials (RCTs) are needed to confirm a possible positive effect of testosterone treatment in infancy before treatment should be offered to all boys with KS

The role of hypogonadism in Klinefelter Syndrome