The question addressed in this clinical trial is whether left-sided donor nephrectomy affects the left adrenal gland. This might be compensated immediately by the contralateral gland or it might lead to a measurable functional adrenal deficit. Such an adrenal insufficiency could be detrimental to the immediate postoperative course. The intermediate-term outcome of the adrenal glands is also of interest, as an impairment of the left adrenal gland will lead to a hypertrophy of the contralateral gland.