Doctor has called for a urine sample due to low adrenal gland numbers in blood test results. what could be causing low adrenal gland numbers?

Many possibilities: A 24 hr urine test is more accurate for the overall level of cortisol in your system, as apposed to a one time check in your blood, since your level of cortisol normally fluctuates throughout the day. Your random check may be normal for the time of day, but it may also be caused by adrenal fatigue, an autoimmune disease, or rarely, tumors.