Medically reviewed by
Dr. Minako Abe, M.D., Board-certified emergency medicine physician researching the relationship between lifestyle and disease onset in relation to the immune system and cancer, Japan
Believe it or not, babies are born with about 300 bones! A baby has more bones than an adult because this allows the baby’s skeleton to be more flexible. This flexibility allows for easier passage through the birth canal and makes babies less prone to fractures. As they grow, some of these bones gradually fuse together, resulting in 206 bones in adults. This dynamic process creates a stronger and more stable skeletal structure suitable for the physical demands of adult life.
Even after these fusions, our bones remain dynamic and versatile throughout life. They provide structural support, protect our internal organs, make movement possible, store essential minerals like calcium, produce blood cells in the marrow, and play a role in endocrine regulation.
Several hormones in the body influence how bones are formed, maintained, and repaired. Estrogen and testosterone help maintain bone density, while parathyroid hormone and calcitonin regulate calcium levels in the body, affecting bone metabolism. Cortisol, produced during stress, can decrease bone formation. Hormonal balance and bone health are, therefore, interconnected.
In this article, our focus is on the relationship between thyroid hormones and our bones. To better understand this connection, we will answer the following questions:
What are thyroid hormones?
Thyroid hormones are chemical messengers produced by your thyroid gland, a butterfly-shaped gland located in your neck. The thyroid produces calcitonin, and thyroid hormones:
- Thyroxine (T4): This is the most abundantly produced hormone by the thyroid. It is also the relatively inactive form of the thyroid hormone and gets converted into T3 in your body tissues.
- Triiodothyronine (T3): While less abundantly produced, T3 is the more active form of the thyroid hormone and is responsible for most of the effects of the thyroid on your body’s functions.
These hormones help regulate many essential bodily functions, including heart rate, body temperature, and body metabolism. They are also necessary for proper growth and development, especially in children and adolescents. Thyroid hormones influence bone growth, brain development, and overall organ function.
The production of thyroid hormones is controlled by a feedback loop involving the hypothalamus (located deep within your brain), the pituitary gland (located near the base of your brain), and the thyroid gland itself.
How does thyroid dysfunction affect bone health?
Before we address the impact of thyroid disorders on bone health, let’s first briefly explain a few terms: osteoblasts, osteoclasts, and bone turnover.
Osteoblasts are cells responsible for bone formation, while osteoclasts are cells involved in bone resorption (breakdown).
Bone turnover is a fancy way of saying that your bones are constantly being broken down and rebuilt. This is a normal and healthy process that happens throughout your life, with each bone turnover cycle lasting about 150–200 days. What’s even more interesting is that you essentially get a new skeleton every 10 years due to this bone remodeling process.
Because thyroid hormones play a role in this transformative process, a significant thyroid dysfunction is capable of having a negative impact on your bone health.
Here’s how this happens:
1. Hypothyroidism and Bone Health
When untreated, hypothyroidism, a condition often characterized by low thyroid hormone levels, can lead to a slowed bone turnover as the activity of both osteoblasts and osteoclasts decreases (but at slightly different rates), calcium levels drop, and bone formation is impaired.
It’s also important to point out that more than hypothyroidism itself, the treatment for hypothyroidism can potentially be more detrimental to bone health. This is likely to happen in overtreatment with levothyroxine, resulting in thyroid hormone levels that are higher than normal, causing hyperthyroidism-induced effects on your bones.
2. Hyperthyroidism and Bone Health
Hyperthyroidism, a condition characterized by excessive thyroid hormone levels, is associated with high bone turnover. Elevated thyroid hormone levels cause osteoclasts to break down bone too quickly, while osteoblasts struggle to keep up. Over time, this can lead to weakened bones and an increased risk of osteoporosis, a condition that makes bones more fragile and prone to fractures.
What are some management and prevention strategies?
If you have a thyroid condition (typically hyperthyroidism or hypothyroidism), here are some practical ways you can protect your bone health:
- Comply with your treatment regimen: The treatment outcomes for thyroid disorders are usually very good if the disorder is detected early and the patient adheres to the treatment plan. This is a good way to reduce the risk of thyroid-induced bone loss or fracture. Even if your thyroid condition isn’t caught early, by adhering to treatment and with regular monitoring of your thyroid function, your bone health risks can still be minimized. Your doctor might recommend a bone density scan (DEXA scan) to assess your bone strength and fracture risk if you have a history of bone disease or some risk factors for osteoporosis. This helps your doctor adjust your medication dose effectively to ensure that your thyroid hormone levels are within the normal range. Once your thyroid hormone levels are back to normal, bone loss often slows down. Sometimes, bone density can even improve as well.
- Take interest in how your medication affects your thyroid hormone levels: It’s been well established that in order to mitigate thyroid-induced bone problems, the underlying thyroid problem has to be properly treated. This means that if your medication dosage isn’t well optimized, you may still face problems with your bone health. A study published in the Journal of Preventive Medicine and Public Health in 2014 found that elderly women with a history of osteoporosis who took high daily doses of levothyroxine were more likely to experience fractures compared to women taking lower doses. This risk was even greater for women who were also taking osteoporosis medications. According to the Royal Osteoporosis Society, thyroid hormone replacement medication (levothyroxine) doses should be carefully monitored in elderly individuals who are at risk of bone loss and fracture.
- Choose a diet rich in calcium and vitamin D: Calcium acts as a building block for bones, and vitamin D helps the body absorb it. Our bodies store a significant amount of calcium, between 1.5 and 2% of our weight. About 99% of the body’s calcium is found in bones and teeth. Calcium combines with inorganic phosphate to form hydroxyapatite crystals which give bones their strength and structure. Unlike vitamin D which can be produced by your body when the skin is exposed to the sun, calcium cannot be made by the body. We need to get calcium from our diet. Make sure to include dairy products, leafy greens, and calcium-fortified foods in your diet. If you have a thyroid disorder and are at risk of osteoporosis, your doctor may recommend calcium and vitamin D supplements. This may be based on an assessment of your condition, whether you’re getting enough of these nutrients from your diet, or if you’re getting enough sunlight.
- Try some healthy lifestyle modifications: Maintaining a healthy weight is a very important aspect of protecting both your thyroid health and bone health. Research shows that being overweight or underweight can affect your bone health negatively. To avoid this, adopt healthy eating habits and consider engaging in safe weight-bearing exercises (such as walking and jogging) or strength training, as these can help increase muscle strength, enhance balance and posture, and reduce the risk of fractures. Also, if you smoke or consume large amounts of alcohol, it’s best to quit. Neither smoking nor excessive alcohol consumption does your bones any good.
Key takeaways
- Thyroid health and bone health are connected. Thyroid hormones play a key role in bone metabolism and turnover.
- By interacting with bone cells such as osteoblasts and osteoclasts, thyroid hormones influence the growth and development of bones, as well as the maintenance of bone density throughout life.
- Osteoporosis is a condition characterized by low bone density and increased bone fragility, leading to an increased risk of fractures. Hyperthyroidism (if left untreated for long) and hypothyroidism (to some extent) can contribute to the development of this bone condition.
- Early diagnosis and proper management of thyroid disorders are essential to maintain strong bones and reduce your risk of bone fractures.
- Always consult your doctor for personalized guidance on managing your thyroid health and bone health. By working closely with your doctor and adopting healthy lifestyle habits, you can support both your thyroid and your bones.
- Adequate calcium and vitamin D intake, along with appropriate weight-bearing exercises, can support bone health in individuals taking thyroid medications.
