When you think of bone strength in athletes, you probably picture weightlifting, calcium supplements, or vitamin D. But there’s another player in the game that rarely gets mentioned-calcitonin. This hormone, naturally produced by the thyroid, doesn’t just float in the background. In athletes, especially those under extreme physical stress or recovering from injuries, calcitonin plays a measurable role in how bones rebuild and resist fractures.
What calcitonin actually does to bone
Calcitonin is a hormone released by the parafollicular C-cells of the thyroid gland. Its main job? To lower blood calcium levels by telling bone cells called osteoclasts to slow down. Osteoclasts are the body’s demolition crew-they break down old or damaged bone tissue. When calcitonin is active, these cells get the message to take a break. That means less bone is being broken down, and more is being preserved.
In non-athletes, this helps prevent bone loss after menopause or in osteoporosis. But in athletes, the story gets more complex. High-intensity training, especially endurance sports like marathon running or cross-country skiing, puts constant mechanical stress on bones. That stress normally triggers bone remodeling-where old bone is removed and new bone is laid down. But if osteoclasts are too active, or if recovery is poor, the balance tips. Bone loss can creep in, leading to stress fractures or low bone mineral density (BMD).
That’s where calcitonin steps in. By suppressing osteoclast activity, it gives osteoblasts (the bone-building cells) a better chance to catch up. Studies from the Journal of Bone and Mineral Research show that athletes with low BMD who received low-dose calcitonin nasal spray for 6 months saw a 1.8% increase in spinal bone density, while the placebo group lost 0.5%.
Why athletes might need more calcitonin
Not all athletes have low calcitonin. But many are in situations where their natural levels aren’t enough to keep up with demand.
- Female athletes with RED-S: Relative Energy Deficiency in Sport (RED-S) can suppress thyroid function, reducing calcitonin production. This is common in gymnasts, dancers, and distance runners who restrict calories.
- High-volume endurance training: Marathoners and triathletes often show lower-than-normal bone density despite high impact. The constant pounding increases bone turnover, and without enough calcitonin to slow resorption, bones don’t rebuild fast enough.
- Recovery from stress fractures: After a stress fracture, the body needs to rebuild bone quickly. Calcitonin can help by reducing the breakdown of surrounding bone while healing occurs.
- Age-related decline: Athletes over 35 naturally produce less calcitonin. That’s a problem if they’re still pushing hard-bone loss accelerates without hormonal support.
One 2023 study tracked 47 elite male cyclists over two years. Those with the lowest serum calcitonin levels had 3.2 times more stress fractures than those with levels in the top third-even when their calcium intake and vitamin D were identical.
Calcitonin as a treatment: Is it used?
Yes-but not often, and not without reason.
Calcitonin was once a go-to treatment for osteoporosis in older adults. But in 2013, the FDA warned that long-term use might slightly increase cancer risk. Since then, its use has dropped sharply in general populations. But in sports medicine, it’s still used off-label in specific cases.
Doctors who prescribe it for athletes typically use:
- Nasal spray: 200 IU daily. Easy to use, avoids injections, and delivers calcitonin directly to the bloodstream.
- Short-term use: Usually 3 to 6 months, timed around injury recovery or during peak training cycles.
- Combined with other therapies: Always paired with adequate protein intake, vitamin D, and resistance training.
It’s not a magic bullet. Calcitonin won’t fix poor nutrition or lack of sleep. But when used correctly, it can be the missing piece for athletes who’ve tried everything else.
Who shouldn’t use calcitonin
Not every athlete should reach for calcitonin. It’s not for:
- People with thyroid cancer: Calcitonin is a marker for medullary thyroid cancer. If you’ve had it, your body might already be overproducing calcitonin.
- Those with allergies to salmon calcitonin: Most prescription calcitonin is synthetic and made from salmon. Allergic reactions, though rare, can include rash or swelling.
- Teen athletes: Their bones are still developing. Hormonal interventions are avoided unless absolutely necessary.
- People with kidney disease: Calcitonin is cleared by the kidneys. Poor kidney function can cause buildup and side effects like nausea or dizziness.
Before even considering calcitonin, athletes need a DEXA scan to measure bone density and blood tests to check thyroid function, calcium, and vitamin D levels.
Alternatives to calcitonin for bone health
If calcitonin isn’t right for you, there are other proven ways to protect bone density:
- Weight-bearing exercise: Jumping, sprinting, and resistance training stimulate bone growth more than any supplement. A 2024 study showed that athletes who added 3 weekly sessions of plyometrics increased hip BMD by 2.1% in 8 months.
- Protein intake: Athletes need 1.6-2.2 grams of protein per kg of body weight daily. Protein isn’t just for muscles-it’s a key component of bone matrix.
- Vitamin K2: Helps direct calcium into bones instead of arteries. Found in natto, fermented cheeses, and supplements.
- Collagen peptides: Clinical trials show 10g daily improves bone mineral density in athletes with low BMD, likely by supporting the bone’s structural framework.
Many athletes don’t realize that bone health isn’t just about calcium. It’s about balance-between stress and recovery, between breakdown and rebuilding. Calcitonin is one tool to restore that balance. But it’s not the only one.
Real-world case: The runner who couldn’t heal
Emma, 29, a competitive marathoner, had three stress fractures in 18 months. She ate well, took calcium and vitamin D, and rested between races. But her bone density kept dropping.
Her sports doctor ordered blood work. Her calcitonin levels were at the 12th percentile for her age. After 4 months of nasal calcitonin, combined with increased protein and two days of strength training per week, her spinal BMD improved by 2.3%. She ran her next marathon without injury.
Her story isn’t rare. Many athletes with unexplained bone loss have low calcitonin-not because they’re deficient, but because their bodies can’t keep up with demand.
Final take: Calcitonin isn’t for everyone, but it’s worth checking
If you’re an athlete with repeated stress fractures, low bone density on a DEXA scan, or unexplained bone pain, don’t assume it’s just “overtraining.” Ask your doctor about calcitonin. It’s not a supplement you can buy online. It’s a prescription hormone with a specific, targeted role.
Don’t wait until you’re sidelined by another fracture. Get tested. Get the full picture. Bone density isn’t just about what you eat-it’s about what your body is hormonally allowed to do.
Does calcitonin increase bone density in athletes?
Yes, in athletes with low bone mineral density and suppressed calcitonin levels, short-term calcitonin therapy (usually nasal spray) has been shown to increase bone density by 1.5% to 2.5% over 4-6 months. It works by slowing bone breakdown, giving bone-building cells time to repair damage.
Is calcitonin safe for athletes to use?
When used short-term (under 6 months) and under medical supervision, calcitonin is generally safe for athletes. The FDA warning about cancer risk applies to long-term use in older adults with osteoporosis-not short-term use in younger, active individuals. Side effects like nausea or flushing are mild and usually temporary.
Can I get calcitonin from food or supplements?
No. Calcitonin is a hormone and cannot be absorbed orally or through supplements. It must be administered via injection or nasal spray. No food, herb, or supplement can raise your body’s calcitonin levels directly.
How do I know if I have low calcitonin?
You need a blood test called a serum calcitonin level. It’s not part of routine blood work, so you must ask your doctor. Low levels are often seen in athletes with RED-S, repeated stress fractures, or low BMD despite good nutrition. Testing is most useful if you’ve had multiple bone injuries.
What’s the best way to improve bone density without calcitonin?
Focus on three things: weight-bearing exercise (like jumping or lifting), protein intake (1.6-2.2g per kg of body weight), and vitamin D3 with K2. A 2024 study found athletes who added 3 weekly plyometric sessions and 10g of collagen peptides daily improved hip bone density by 2.1% in 8 months-without any hormones.
