It could be either of these issues. My mother and aunt suffer from diabetes, and I suffer from a thyroid problem. I know my mom and aunt get sleepy and/or cranky when their sugar is low, but that's as far as my expertise with the diabetes goes. As far as the thyroid, the crankiness when you're hungry, and the depression could very well be caused by a thyroid problem. If you have major mood swings, are very sensitive to heat and/or cold, excessive weight gain or loss, trouble sleeping, trouble concentrating, hair loss, dry skin, or a number of other issues, it could very well be your thyroid. The best way to find out for sure is to go to your doctor, tell them your symptoms and ask them to test both your thyroid (T3, T4 and TSH levels) and your blood sugar. I hope this helps and good luck. You can always double check your symptoms on webmd.com it's a great source of information.