Testosterone increases serum 1,25-dihydroxyvitamin D and insulin-like growth factor-I in hypogonadal men

Summary The short‐term metabolic effects of testosterone treatment on circulating levels of 1,25–dihydroxyvitamin D and insulin‐like growth factor‐I (IGF‐I) were studied in 13 hypogonadal men. The study group included 11 men with Klinefelter's syndrome, with varying degree of androgen deficiency, and two men with secondary hypogonadism. Pretreatment levels of 1,25–dihydroxyvitamin D, vitamin D‐binding protein and IGF‐binding protein‐I were all within the normal range. The levels of IGF‐I were lower than normal in 5/11 of the Klinefelter patients and in one patient with GH‐deficiency. Testosterone treatment increased circulating total 1,25–dihydroxyvitamin D significantly from 75 ± 4 pmol l‐1 (mean ± SEM) to 86 ± 4 (P