Thyroid Medication and Osteoporosis - How Does Levothyroxine work?
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Does Thyroid Medication Increase Your Osteoporosis Risk?

Oct 24, 2016

Plenty of stories in the popular media link Thyroid medication and osteoporosis levothyroxine (popular names include Synthroid, Levothroid, Levoxyl, Levo-T and Unithroid) to increased osteoporosis and hip fracture risk. Is there any truth in this? Should you be taking calcium supplements?

What Is Hypothyroidism?

Let’s get the basics out of the way first.

Hypothyroidism is a hormonal disorder that leads to a deficiency of the thyroxine hormone produced by the tiny, butterfly-shaped gland that sits in your throat, the thyroid. Thyroxine is indispensable to the body because it regulates several vital functions like growth, development, metabolism and immunity. As we age, the levels of thyroxine slowly deplete resulting in hypothyroidism that affects nearly 4.6% of the population in the U.S.

The most common symptoms of hypothyroidism include persistent fatigue, disturbed sleep cycle, weight gain, hair fall and a weaker immune system that leads to frequent illness like cold, fever and so on. However, there are up to 300 known symptoms of hypothyroidism, some lesser known, so it is a good idea to be aware of these.

The first line of treatment for primary hypothyroidism is an artificial substitute for the thyroxine hormone, called levothyroxine.

How Does Levothyroxine Work?

Levothyroxine is an artificially synthesized replacement for thyroid hormone that stabilizes the Thyroid medication and osteoporosis levels in the blood. It is the number one prescribed drug in the United States, with 23 million prescriptions each year!

The body seems to accept the artificial thyroxine without any overt and drastic reactions. Moreover, since the tablet is free of any color additives and so, potential food allergies are also nonexistent. And yet, there are some doctors who are wary of Levothyroxine because there is research that points out that Levothyroxine may interfere with the absorption of calcium in the body. If this is true, this may cause calcium deficiency and increase the risk of stress fractures.

Why Would Levothyroxine Be Suspected to Cause Hip Fractures?

On an average, there are nearly 2 million hip fractures that occur annually in U.S. One of the long standing controversies in medicine revolves around the adverse impact of levothyroxine on bones, leading to hip fractures.

When the body has too much thyroxine, a condition called hyperthyroidism, this can lead to bones being broken down faster than they can be built back. Every system in the body is connected to others and there is a delicate balance between your Thyroid medication and osteoporosis and the bone builders in your body, called osteoblasts. If there is too much thyroxine in your body for a long time, osteoblasts take this as a message to slow down rebuilding of bones, leading to weaker bones.

Some research studies say too much levothyroxine, which is synthetic thyroxine, could also cause loss of bone; you medicate too much and it weakens the bones.

A 2006 research study conducted in Greece, aimed at assessing the changes in bone mass density in women receiving Levothyroxine treatment post thyroid cancer treatment showed this. The study was conducted on 26 women, for a duration of 48 months and found that the bone mass density was significantly lower in areas like the femoral neck, Ward’s triangle and femoral trochanter.

Other studies were also conducted over time to determine the effect of levothyroxine on calcium absorption. Some of these studies showed that intake of levothyroxine was connected to loss of calcium through the urine.

Too Much Levothyroxine Is The Real Culprit!

Medicating with levothyroxine increases the production of thyroid hormone

Medicating with levothyroxine increases the production of thyroid hormone

When we look at the research closer though, clarity emerges. Too much thyroid hormone, whether it is created naturally in the body or given as a supplement in the form of levothyroxine, can cause weaker bones. So the real culprit is not all levothyroxine, it is too much levothyroxine. This can happen if you don’t test your Free T3 and Free T4 regularly and end up taking too much thyroid medication.

Too often, since thyroid medication is considered to be for life, people stop getting regular tests. This is especially so in senior citizens and this can lead to the dosage of your medication being more than your body needs. The simple rule therefore, is to test your blood thyroid hormone levels every 6 months.

It may well be that since lowered bone density and hypothyroidism occur naturally at the same life stage, (during menopause and andropause for women and men respectively) the two conditions may have been incorrectly correlated by researchers. More recent studies indicate that appropriate amount of thyroxine in the blood does not affect bone density adversely.

Taking Levothyroxine Four Hours Away From Calcium: The Best Solution

From the point of view of simple body chemistry, levothyroxine or synthetic thyroid hormone and calcium don’t go well together. Each interferes with the absorption of the other.

Whether it is dietary calcium, from dairy or other foods or it is supplemental calcium, always keep a 4-hour gap between calcium and your thyroid medications.

A case study in the Canadian Journal of Family Physicians shows how a woman who was suffering from hypothyroidism and was prescribed artificial thyroxine. After about a year, she was also diagnosed with osteopenia. She was then given a daily dose of Calcium carbonate to cure the osteopenia. This did not help as she was consuming both the pills at the same time.

Taking Calcium: Supplement With Care

levothyroxine and calcium levels

levothyroxine and calcium levels

Since loss of bone density happens both to men and women around the age of 50, many are prescribed calcium supplements to keep osteoporosis at bay. This is even more common among women who even self-medicate, since most of us are aware of the menopause-calcium supplements connection.

However, calcium is a mineral that should be supplemented only after proper testing. There is evidence that supplementing blindly with calcium could increase the risk for kidney stones, gastrointestinal problems as well as cardiac diseases.

A detailed study on the effect of calcium supplements on cardiac risks showed that it increased the risk for myocardial infarction (heart attack) and stroke by 27-31%. This could often happen because calcium needs vitamin D, vitamin K and magnesium to all be present in the correct ratio, for it to be absorbed into bones, rather than be deposited in arteries where it can cause calcification or narrowing.

Obtaining calcium from natural sources is a great idea, when possible. Inclusion of rich sources of calcium like low-fat dairy products, green vegetables, oily fish and so on will easily provide you with the required amount of calcium. Little things like allowing your skin to soak sunshine for 20 minutes a day will also help you get your daily dose of vitamin D. As vitamin D and calcium are important associated nutrients, together they will truly prevent hip fractures and Thyroid medication and osteoporosis in the long run. Exercises like Tai Chi too will definitely keep osteoporosis at bay.

The Take-Aways:

If you are on levothyroxine, do the following:

  • Test regularly for your Free T3 and Free T4 levels; the dose of your medication should be adjusted according to these levels. Too much medication can cause weak bones and increased risk of fractures.
  • Ensure you are getting enough calcium. Test and supplement if necessary. Whether you’re getting it from foods or supplements, make sure your calcium intake is at least 4 hours away from your levothyroxine.
  • Always ensure that your calcium supplement is properly balanced with Vitamin D, Vitamin K and magnesium.
 Dr. Rachita Narsaria
Dr. Rachita is a practising doctor with a passion for prose. With over 6 years of medical writing experience for patients and doctors alike, this doctor-cum-entrepreneur loves learning and sharing knowledge.


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