Fathers who take metformin are more likely to have babies who are born with defects, new research suggests.
But experts say the risk only exists if men take the cheap diabetes drugs during conception.
Defects were about 40 percent more common in adolescents whose fathers were prescribed the usual medications.
And the risk of sons having a genital defect was three times higher with 1.1 million newborns, according to the study.
Experts say men who are taking the diabetes drug and plan to have children should talk to their doctors about switching drugs.
However, the team warned that diabetes itself – a condition affecting millions of men – also reduces sperm quality and fertility.
Metformin is usually the first drug prescribed for people with type 2 diabetes. It’s unclear how many men are prescribed the drug, but 4.7 million people in the UK and 37 million in the US have diabetes
Metformin is usually the first drug prescribed for people with type 2 diabetes.
It’s unclear how many men are prescribed the drug, but 4.7 million people in the UK and 37 million in the US have diabetes.
The drug controls type 2 diabetes by reducing the amount of sugar that the liver releases into the body and lowers blood sugar levels by improving insulin resistance.
Academics at the Universities of Stanford and Southern Denmark analyzed 1.1 million births in Denmark between 1997 and 2016.
They compared the newborns’ health records to their fathers’ prescriptions for diabetes drugs such as insulin, metformin and sulfonylureas.
Babies were considered “exposed” to a drug if their father had at least one script in the three months leading up to conception – when the fertilizing sperm were developing.
Of all the babies included in the study, 3.3 percent were born with one or more serious birth defects.
WHAT IS DIABETES?
Diabetes is a lifelong condition that causes a person’s blood sugar levels to become too high.
There are 2 main types of diabetes:
- Type 1 diabetes – where the body’s immune system attacks and destroys the insulin-producing cells
- Type 2 diabetes – when the body does not produce enough insulin or the body cells do not respond to insulin
Type 2 diabetes is far more common than type 1 diabetes. In the UK, around 90 percent of all adults with type 2 diabetes have it.
The amount of sugar in the blood is controlled by a hormone called insulin, which is produced by the pancreas (a gland behind the stomach).
When food is digested and enters your bloodstream, insulin moves glucose from the blood into the cells, where it is broken down for energy.
However, when you have diabetes, your body is unable to convert glucose into energy. This is because there is either not enough insulin to move the glucose or the insulin produced is not working properly.
There are no lifestyle changes you can make to lower your risk of type 1 diabetes.
You can manage type 2 diabetes with healthy eating, regular exercise, and maintaining a healthy weight.
Source: NHS
But the figure was 5.2 percent in newborns whose fathers took metformin, the study in the Annals of Internal Medicine showed.
The team said this represented a 41 percent greater risk compared to those who didn’t take it.
The results also showed that the sons of paternal metformin users were three times more likely to have a boy with genital birth defects.
However, fathers who took the drug before or after trying to conceive did not have an increased risk.
Metformin is believed to suppress male hormones such as testosterone and impair male reproductive health.
And studies have found smaller testicle size and lower testosterone secretion in the offspring of male rats exposed to metformin.
Meanwhile, fathers who took insulin had no increased risk of having a baby with a defect compared to fathers who didn’t take the drug.
There were insufficient data on fathers taking sulfonylureas to determine if they were at increased risk.
The experts said the “sheer size of the diabetes pandemic” suggested the treatment of prospective fathers with diabetes should be further explored.
Professor Allan Pacey, an andrologist at the University of Sheffield and former chairman of the British Fertility Society, who was not involved in the study, said metformin was “a commonly used drug in men of childbearing age”.
So the results raise the question of whether men who are taking the drug and planning to start a family in the near future should be concerned,” he said.
“This should be discussed with their GP or their diabetes specialist,” added Professor Pacey.
Diabetes itself can affect male fertility, so it’s important that men “take some form of medication rather than going off their metformin altogether,” he noted.
dr Channa Jayasena, an andrologist at Imperial College London, said the results were surprising as insulin is a stronger drug than metformin.
He said: “The authors cannot rule out that men on metformin had less control of their diabetes.
“So the results are thought-provoking, but not conclusive. Men with diabetes should not be discouraged from taking metformin, but this is worth looking into.’
Professor Sheena Lewis, an expert in reproductive medicine at Queen’s University Belfast who was not involved in the study, noted that the study did not look at how well the men controlled their diabetes and that poor management had detrimental effects on sperm.
She said: “As couples wait until old age before starting a family, their chances of receiving medication for other chronic diseases increase.
“The takeaway message is that men trying to have children should discuss all other medications with their GP to ensure they have no known adverse effects on male fertility.”