July 8, 2008
Daily Care, Insulin
Question from Swift Current, Saskatchewan, Canada:
Why is it that so many type 1 diabetics need LESS insulin in the early morning? I am very insulin sensitive between 4 and 7 a.m. and need one-third of my usual correction factor or insulin-to-carbohydrate ratio. I also am prone to lows with my usual basal rate at this time. A type 1 friend of mine even turns her pump off between 3 and 4 a.m. What causes this?
Also, why does my correction factor change the higher my blood glucose level goes? For example, my usual factor is much too high once my blood sugar is in the 20 mmol/ls [over 360 mg/dl]. If I take the full dose my pump suggests, I will go low. I need LESS insulin when severely high and I never need more than 3 to 3.5 units to bring down a high reading, even in the 20 mmol/ls [over 360 mg/dl]. Why do pumps not allow for this? There is no way to adjust the correction factor according to blood glucose level. Is this because my pancreas still is making insulin? I have had type 1 for 24 years and my basal rate is 0.5 units per hour. Sometimes I need less than one unit to bring down a high or for food. Often, my glucose level will drop rapidly within minutes after taking my insulin (subcutaneously using my pump). Is it possible my pancreas is trying to “help out” my injected insulin? I can drop from 15 mmol/l [270 mg/dl] to 6 mmol/l [108 mg/dl] in 15 minutes, with all of that insulin still on board. I am very prone to hypoglycemia and seizures. So, I am I just very insulin sensitive or is something else going on? I use 0.42 units per kg of body weight. I think this is “normal” for a person without insulin resistance, like most type 1 diabetics are.
I also have celiac, so I follow a strict gluten free diet, and Hashimoto’s thyroiditis. My thyroid gland is still active from time to time despite 16 years of disease. I avoid soy products and take animal thyroid hormone, which may reduce the autoimmune attack. I also do not eat any milk products (anaphylaxis to milk recently manifested/diagnosed as a adult), which may be reducing autoimmunity against my pancreas. I also take Omega 3 EFA supplements and Vitamin D. I was suspected of having Addison’s multiple times due to my sudden periods of extreme insulin sensitivity/low insulin needs, but this never seems to be the case. I have been in the Emergency Room numerous times. The doctor had never seen a case where a type 1 needed LESS insulin and kept going low for no known reason.
If I still do make insulin from time to time, can I qualify for a “newly diagnosed” study?
Also, why do insulin needs increase during menstruation? Is there a benefit to this in human evolution? Or, is it a by-product of something unintentional, like specific hormones “accidentally” binding to insulin receptor sites?
I will try and answer your questions in order.
As a physician who treats a lot of patients with insulin pumps, and this includes setting the basal rates throughout the day, I would say that it is not universal that patients are extremely insulin sensitive during the early morning hours between 4 and 7 a.m. In fact, as we were learning how to use insulin pumps, the most common time to have to increased basal rate infusion rates is during this time. It is associated with an early morning rise in cortisol and growth hormone, the hormones that antagonize insulin’s effects. I would say at least one-third of all people need this step up in insulin dosing. In addition, investigators that have looked at exercise and the potential of hypoglycemia point to the early morning as the best time, as those patients with type 1 diabetes receiving intermittent injections have their lowest insulin levels of the day and are less likely to get low. As we look at your case, and that of your friend, it would be helpful to know a little bit about your lifestyle. Are you physically active? It is known that the effect of exercise can roll over hours after you have been active. Do you tend to run lower earlier in the night? It would help to know what your sugars do before the 4 a.m. time. However, all this being said, you may have less hormone antagonism of insulin.
It takes more insulin to bring the glucose levels down after they have gotten high, compared to maintaining them at a lower level. This is a common observation. It is a good thought.
I think you are likely to be very insulin sensitive.
As far as studies go, I think your best bet is explore the NIDDK web site that lists the studies that are available for participation and that are sponsored by NIH funding.
As far as increased insulin requirements during menstruation, you need to know that the hormones estrogen and progesterone are changing during the menstrual cycle. During the latter half of the cycle, levels of progesterone rise. It is known that progesterone can induce insulin resistance. This same phenomenon exists in women who use birth control pills as the pills contain a progesterone at higher concentrations during the latter half of the cycle. Clinically, this entity is more prominent in some women than others. Not everyone has to increase their rates during their periods.
[Editor’s comment: For a list of clinical trials for type 1 diabetes in Canada see ClinicalTrials.gov