Question

In my late teens I started spilling sugar in my urine. I had numerous glucose tolerance tests that were all normal. I was told I had a 'low renal threshold'. Does this make me more prone to developing diabetes? I'm now 47, 40 pounds overweight and tired all the time. I've also been treated for depression following my father's death and losing the vision in my right eye due to optic neuritis/atrophy. Can you help me?

Answer

Simply stated, the renal threshold is the concentration level up to which a substance (such as glucose) in the blood is prevented from passing through the kidneys into the urine. If you have a low renal threshold this means is that your kidneys allow glucose to spill into your urine at a level lower than normal. This does not make you more prone to have, or to develop diabetes. This may be difficult if you are in a doctor's office and your urine is routinely checked and found to have sugar. Your doctor might assume that you have developed diabetes. A serum sugar done at the time of your urine sample would show your blood sugar to be normal.

Having a low threshold for glucose and spilling glucose in the urine is called renal glycosuria. It is a benign (harmless) condition, seen in 0.2% to 6% of people in the USA, according to different surveys. In very rare cases, it may be associated with ocular changes - cataracts or glaucoma (Lowe syndrome, occurs in infancy) or a Kayser-Fleischer ring of copper deposits in the eye (Wilson disease) - but neither of these fit with your eye problem.

Nevertheless, remember that being overweight is a risk factor for developing diabetes! Do something about your weight!