Could Rampant High Glucose Intolerance among Parkinson’s patients lead to an increased risk of diabetes? : By Dr. De Leon

The other day, I had a follow up with my endocrinologist because I have been concerned about a slowly increasing sugar levels as well as HgA1C (glycosylated Hemoglobin used to detect sugar levels in the last 3-6 months to help diagnose diabetes and then gauge management) possibly being caused of increased night sweats and overall sweating.

Although I am not diabetic, I am becoming slowly at risk…which initially I attributed my increase glucose levels to the number of steroids I have received over the past 12 months for treatment of various other illnesses.

Then I began to wonder if this process had anything to do with my Parkinson’s?

I then seemed to remember reading something about dopamine increasing sugar levels and tried to recall by first year of medical school when we discussed physiology.

After my visit my doctor confirmed that I was becoming glucose intolerant and would be best to start treatment to avoid developing diabetes. Well of course this was not a pleasant experience to add yet another medication to my already long list of medicines but more importantly sent me in search of answers?

What I discovered to my great astonishment and chagrin was that indeed there is a connection between having Parkinson’s, dopa intake and developing insulin resistance leading to diabetes. What amazed me the most was study after study detailing this information dating back to the late seventies; yet no one in neurology or Parkinson’s specialty much less others outside this field have ever made any comments, concerns, or indications to monitor a patient’s sugars or discuss risk of diabetes!!!!

In the presence of high sugars, dopamine stimulates insulin secretion from pancreatic cells. (1)

The substancia nigra plays a crucial role in controlling structure and activity of these pancreatic islet cells which produce insulin. When lesions occur in this area of the brain or there is loss of dopamine there is a decrease in the content of insulin thus unable to properly regulate blood glucose levels causing an increase? This process is mediated via D2 receptors in the pancreas. However, as with all things pertaining to the brain things are not always straight forward. At increased concentrations outside of the brain it has an inhibitory role while it stimulates insulin at lower concentrations.

This perhaps can be the simplest explanation of why Parkinson’s patients have increased chocolate cravings particularly when off or low on dopamine, as has been my experience, in an attempt not only to increase dopamine but more importantly to increase glucose levels. This information again perhaps is one of the reasons a blood glucose modifying agent was studied to see its effects on PD as disease modifying. (2)

Studies have shown higher fasting blood glucose levels in 50 to 80% PD patients than in normal (non-PD) patients suggesting again that there may be an impairment in glucose tolerance (or glucose intolerance) problem. This problem may be further exacerbated by levodopa therapy (3); yet to date this issue has been mostly ignored leaving the risk of developing diabetes in a Parkinson’s patient completely undefined. I highly believe that high glucose intolerance merits high scrutiny as well as further research considering the irreversible damage diabetes can cause in an already fragile health system leading to increase dyskenesias, poorly controlled motor symptoms and less than effective treatment with levodopa.


  • Thus, I urge each and every Parkinson’s patient to discuss this important issue with your physician/ MDS/ neurologist.
  •  frequent fasting sugar monitoring and or HgA1C testing particularly if at risk for Diabetes due to other factors like obesity or family history.
  •   if found to have glucose intolerance, as I have, initiate treatment for the hyperglycemia. I am now on metformin XR. Keep you posted regarding PD symptom changes- I will see if sweating decreases.


  1. E. Shankar, KT. Santhosh and CS. Paulose. (March 2006): Dopaminergic Regulation of Glucose-induced Insulin Secretion through Dopamine D2 Receptors in the pancreatic islets in Vitro. Life 58(3):157-163 
  2. Robert Preidt (July 2015) “Common Diabetes meds & Lower Risk for Parkinson’s.” WebMD News Health Day. 
  3. R. Sandyk (March-April 1993) “The relationship between diabetes mellitus and Parkinson’s disease. Int J Neurosci.69 (1-4):125-130

6 thoughts on “Could Rampant High Glucose Intolerance among Parkinson’s patients lead to an increased risk of diabetes? : By Dr. De Leon

  1. I was diagnosed with type 1 diabetes at age 48 in 2007 as well as Hashimoto (hypothyroid). About 4 months ago my neurologist determined that the 2 year long shaking of my left arm could very well be Parkinson’s. Well, after 1 month on Sinemet the shaking stopped. I now have two side effects showing up from the Sinemet – excessive sweating and in a considerable increase in my blood glucose levels – basically, it seems as if the Sinemet is increasing my resistance to insulin.

    1. I am sorry you are having to go through all this as well ..yes dopamine blocks production of insulin so would make sense sugar levels would increase …talk to doctor about adjusting blood glucose meds..also although swearing may very well be related to fluctuating sugar levels…I find that sweating usually occurs at lowest point of dopamine…i.e. When medicine has worn off…hope this helps and best of luck…keep a diary of both symptoms and discuss with both endocrinologists and neurologists

  2. Very interesting. I’ve had Parkinson’s & Type 2 diabetes for several years & now take Metformin. I had DBS 2 years ago & my weight & A1C soared. Weight gain is a known side effect of DBS. However, DBS was a great success in that it totally fixed my horrendous tremor, though my walking, balance, speech & language are much worse. I’ve always craved sugar & “treat” my symptoms with something sweet, especially chocolate. It feels as if I need more sugar in my brain. I feel better, more up, not so depressed. What to do, what to do? I wish I knew the best course of action. There’s something going on, but what?

    1. Hi paula, thanks for sharing your story…i too gained lots of weight partially because meds increase weight and water retention and the dreaded sugar cravings which is a way our bodies/ brain tells us me need more dopamine i believe. once i upped my dopamine replacement the cravings disappeared but not the weight. i recently started taking victoza for weight and sugar control and feel so much better. talk to your physician and hope you get to feeling better soon.

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