Metformin is a drug commonly used to treat type 2 diabetes by controlling the amount of sugar in the blood. Now, a new study suggests patients with under-active thyroids who take metformin have an increased risk of low levels of thyroid-stimulating hormone.
Metformin, a commonly used medication for type 2 diabetes, could increase risk of low levels of TSH, researchers say.
Having an under-active thyroid - also known ashypothyroidism - means that the thyroid gland does not make enough thyroid hormone to meet the body's needs. The thyroid hormone regulates the metabolism, affecting almost every organ in the body.
Low levels of thyroid-stimulating hormone (TSH), which is excreted by the pituitary gland, can cause serious damage, including cardiovascular conditions and fractures.
Metformin is used either alone or in combination with other medications, such as insulin, to treat type 2 diabetes by decreasing the amount of sugar absorbed from food and the amount made by the liver.
Long-term diabetes and high blood sugar can develop into serious or life-threatening complications, such as heart disease, stroke, kidney problems, nerve damage and eye problems.
However, previous research has suggested that metformin could lower TSH levels, potentially exposing patients to harmful effects of subclinical hyperthyroidism.
As such, the researchers of this latest study, led by Dr. Laurent Axoulay of McGill University in Montréal, Canada, examined data on 74,300 patients who received metformin and sulfonylurea - another common drug for diabetes - over a 25-year period.
They publish their results in the Canadian Medical Association Journal (CMAJ).
'Metformin linked to 55% increased risk of low TSH levels'
Of the study participants, 5,689 had been treated for hypothyroidism, while nearly 60,000 had normal thyroid function. Among the hypothyroidism group, there were 495 cases of low TSH per year, compared with 322 in the normal group.
The researchers found that in patients with treated hypothyroidism, metformin use was linked with a 55% increased risk of low TSH levels, compared with the use of sulfonylurea.
Fast facts about hypothyroidism
Without enough thyroid hormone, the body's functions slow down
In the US, around 4.6% of the population over 12 years old have hypothyroidism
Symptoms include fatigue, weight gain, cold intolerance,constipation, impaired fertility and depression.
The team adds that use of metformin did not appear to affect those with normal thyroid function.
They conclude that their findings "support the hypothesis that metformin may lead to reductions in TSH levels in patients with treated hypothyroidism."
Dr. Axoulay adds:
"Given the relatively high incidence of low TSH levels in patients taking metformin, it is imperative that future studies assess the clinical consequences of this effect."
Though their study had a large sample size, there were certain limitations. For example, their data showed records of prescriptions written by physicians, but it is unknown whether the patients followed the treatment. However, the researchers say prescription renewals were "likely good indicators of adherence."
They add that given the observational nature of the study, residual confounding needs to be considered, despite the fact that consistent results were observed.
Medical News Today recently reported on a study that suggested metformin could increase the lifespan of non-diabetic individuals.
Statins are drugs that lower cholesterol in the body by interfering with the production of cholesterol in the liver. Though they lower bad cholesterol and raise good cholesterol, one side effect is that they increase risk of diabetes. Now, researchers have discovered why and offer a way to suppress this side effect.
One of the world's most widely used drugs, statins have been hailed by the medical community for their ability to prevent heart disease.
Still, the researchers, who have published their findings in the journal Diabetes, were confused as to why diabetes was linked to statin use.
"Recently, an increased risk of diabetes has been added to the warning label for statin use," says lead author Jonathan Schertzer, assistant professor of Biochemistry and Biomedical Sciences, and Canadian Diabetes Association Scholar.
"This was perplexing to us," he continues, "because if you are improving your metabolic profile with statins you should actually be decreasing the incidence of diabetes with these drugs, yet, the opposite happened."
According to the team, around 13 million people could be prescribed a statin drug at some point in their lives.
In January of this year, the Food and Drug Administration (FDA) released a Consumer Update outlining some of the risks associated with taking statins, which included an increased risk of raised blood sugar levels and the development of type 2 diabetes.
At that time, Dr. Amy G. Egan, deputy director for safety in the FDA's Division of Metabolism and Endocrinology Products, said:
"Clearly we think that the heart benefits of statins outweighs this small increased risk. But what this means for patients taking statins and the health care professionals prescribing them is that blood-sugar levels may need to be assessed after instituting statin therapy."
But until Prof. Schertzer and his team conducted their latest research, the pathway linking statins to diabetes was unknown.
Glyburide taken with statins suppressed immune response
After investigating further, the research team found that statins "activated a very specific immune response, which stopped insulin from doing its job properly," says Prof. Schertzer.
After "connecting the dots," he and his team discovered that taking another drug - called glyburide - alongside statins suppressed this immune response.
Though statins can prevent heart disease by lowering cholesterol, they also increase risks for developing type 2 diabetes.
This finding could yield the development of new targets for this immune pathway that do not interfere with the positive effects of statins, they say.
For future research, Prof. Schertzer and colleagues want to understand how statins advance diabetes by understanding how the drugs work in the pancreas, an organ that secretes insulin. Other side effects include muscle pain and muscle breakdown, and the team hopes to understand whether the immune pathway is involved in such side effects.
"It's premature to say we are going to change this drug," says Prof. Schertzer, "but now that we understand one way it can cause this side effect, we can develop new strategies to minimize side effects."
He adds that they could even possibly use natural products or strategies involving nutrition to counter these side effects.
Because statins are so widely prescribed, the researchers say understanding how they prompt adverse effects could lead to vital improvements in the drug, which could ultimately affect a large portion of the population.
Prof. Schertzer concludes by noting:
"With the new federal warning label on the risk of diabetes with statin usage, people are heavily debating its pros and cons. We think this is the wrong conversation to have. Statins are a great drug for many people. What we really should be talking about is how to make them better, and we are beginning to understand the basic biology of statins so we can do just that."
Medical News Today recently reported on a study that suggested patients with terminal illnesses benefit from stopping statins. Researchers from that study said patients in late stages of cancer or other terminal illnesses may extend their lives by discontinuing use of the drug.