The thyroid is a small gland found in the neck that produces hormones needed for various purposes.
Some of these hormones affect things such as heart rate and body temperature.
Therefore, any problems with your thyroid can have a huge effect on the body.
The most common thyroid issues are having an underactive thyroid (hypothyroidism) or an overactive thyroid (hyperthyroidism).
As the name suggests, an underactive thyroid occurs when your thyroid gland does not produce enough hormones.
Some of the most common symptoms include feeling tired or depressed and weight gain.
However, according to the NHS, these symptoms are “often similar to those of other conditions”, and typically develop slowly, “so you may not notice them for years”.
If you suspect you have an underactive thyroid one expert shared a simple technique to be sure.
In a video posted to his YouTube channel, health expert Dr Eric Berg recommended the Achilles tendon test for this very reason.
Speaking to his 11.2 million subscribers, he explained how people with hypothyroidism will experience a different reaction when their Achilles tendon is knocked, compared to those without the condition.
“Another test that you can do for classic hypothyroidism is the Achilles tendon test,” he said.
“You can take a little hammer, the one that you would check your reflexes with and just tap the Achilles tendon or get someone to tap it.”
Dr Berg related the crucial difference to spot.
He said: “Now normally what happens if you’re laying down flat and your foot is hanging down and you tap this little Achilles tendon here, it should do this, right?”
He indicated to a foot that shot up and down very quickly.
Instead, if you have an underactive thyroid the foot will take a while to come back down.
“So what happens with hypothyroidism is it will do this, but it won’t come down that fast,” Dr Berg said.
“So it’s that return action that’s going to be sluggish. And that would be a good test to determine if you truly have a primary thyroid problem.”
His advice is backed by a case study report, published in the Canadian Medical Association Journal in 2008.
It documented how a 55-year-old woman with hypothyroidism displayed “delayed relaxation of deep tendon reflexes in her upper and lower limbs”.
According to the report, 75 percent of patients with the condition experience delayed reflexes in this way.
If you are concerned that you could have an underactive thyroid you should speak to your GP.