Klinefelter's syndrome, type 2 diabetes and the metabolic syndrome: the impact of body composition

Klinefelter's syndrome (KS) is the most common sex-chromosome disorder in men, affecting ∼1:660 men, and is a rather common cause of infertility, hypogonadism and learning disability. Traditionally, men with KS have been described as tall, slim, narrow shouldered, broad hipped, with hypergonadotrophic hypogonadism and small testes. Recent studies showed an increased risk of diabetes and an unfavourable change in body composition; with accumulation of body fat and decreased muscle mass and a concomitant decrease in insulin sensitivity, muscle strength and oxygen consumption capacity. Here, we review the data on body composition, insulin resistance and metabolic syndrome in relation to testosterone in both KS patients and normal men. Treatment with testosterone in hypogonadal states (other than KS) seems to improve body composition in both clinical and experimental studies. Despite the lack of such studies in KS, we recommend testosterone treatment to KS patients with low serum testosterone or increased LH and change in body composition.