Pituitary testicular axis function and sex hormone binding globulin binding capacity in thalassaemia major.

Pituitary testicular function was investigated in 19 prepubertal and in 5 pubertal male thalassaemic patients. Total plasma testosterone in prepubertal and in pubertal patients was significantly lower than in controls. In the prepubertal thalassaemics, the lower total testosterone concentration correlated with the diminished sex hormone binding globulin binding capacity (SHBGcap), and the free testosterone levels were normal. The lower testosterone is probably due to the damaged liver function rather than to a diminished testicular function. In the pubertal patients, the testosterone reduction is equally due to the SHBG bound testosterone fraction and the free testosterone fraction. Basal and LHRH stimulated plasma gonadotrophin levels were also significantly decreased in the pubertal subjects. The observed hypotestosteronemia in the pubertal thalassaemics seems to depend on the impaired pituitary gonadotrophin secretion probably due to the chronic iron overload.