Understanding bone loss in menopause and beyond
Bone health is imperative as we age, and is especially important as we go through menopause. Bone loss starts to occur slowly after the age of 35, and by the time perimenopause has started and oestrogen levels start to fluctuate, it can occur more rapidly. Oestrogen plays an important role in bone strength and prevents bone loss – menopausal women are at risk of developing osteopenia and osteoporosis due to the overall decline in oestrogen and other factors. The average woman loses up to 10% of her bone mass in the first 5 years of post menopause.
Osteoporosis is more common in women as they age than men. Data provided by the Australian Bureau of Statistics (ABS) shows that in 2017-18, 29% of women aged 75 or older had osteopenia or osteoporosis compared to 10% of men in the same age group. In fact, the percentage of women affected by bone loss increases as they age shown by other data in 2017-18 from the ABS – 4.4% aged 45-54, 13% aged 55-64 and 21% aged 65-74.
What the heck is a
t-score and z-score?
Bone mineral density (BMD) is tested using a DEXA scan, which involves quite a lot of statistics in determining the density of bone. There are two scores derived from the equations, t-score and z-score. Without boring you with the statistics:
- The t-score is where your BMD is compared to healthy, young adults aged between 25-35 years or your same sex and ethnicity
- The z-score is where your BMD is compared to adults the same age and sex as you.
T-scores are predominantly used to determine your rate of bone loss, or your risk of future fracture. Positive t-scores indicate that your bone is stronger than normal, and negative t-scores indicate that your bone is weaker than normal. Basically, the t-score determines normal bone density, osteopenia (low bone density), or osteoporosis (high risk of fracture). Below is a table that outlines the t-score values that would be included in your DEXA scan results from your doctor:
| Bone Mineral Density | T-score |
| Normal | Positive t-score |
| Osteopenia (low bone density) | -1.0 to -2.5 |
| Osteoporosis | -2.5 or higher |
What is bone loss exactly?
Before we look at bone loss and how it happens, we need to understand the structure of bones. Bones are composed of two types of tissue:
- Compact bone (hard), the strong, durable bone that makes up the outer layer
- Trabecular bone (soft), the spongy, lighter and less dense inner bone, resembling honeycomb
Also found in bones are specialised cells that function to build bone up (called osteoblasts) and break bone down (called osteoclasts), collagen and other proteins, nerves and blood vessels, bone marrow, cartilage and bone minerals – mainly calcium and phosphate.
The specialised cells involved in building new bone (osteoblasts) and breaking bone down (osteoclasts) are part of a highly regulated system of a continuous bone remodelling cycle. This is a lifelong process that occurs every 120-200 days for both hard and soft bone, preserving the bone and maintaining the balance of calcium and phosphate, hardening the bone and giving it strength.
It is when an imbalance of the bone remodelling cycle occurs, that low bone density, or osteoporosis can be seen. There are many regulators involved in the bone remodelling cycle, including Vitamin D, cytokines and sex hormones, to name a few.
Vitamin D is involved in the regulation and absorption of the calcium and phosphate from the food that we eat. Oestrogen is the main sex hormone involved in the regulation of the bone remodelling cycle. Oestrogen deficiency, as seen in postmenopause, uncouples the action of the buildup and breakdown of bone, essentially causing the bone breakdown to occur much faster than the bone building up – resulting in low bone density – osteopenia or osteoporosis. Oestrogen deficiency also results in an increase in cytokines that result in the increased breakdown of bone also.
What is osteopenia?
Osteopenia is the precursor to osteoporosis. It is low bone mineral density or thinning/weaker bones, that sits somewhere between normal and osteoporosis after having a DEXA scan. Not everyone who has osteopenia will develop osteoporosis, but it is a warning sign that action needs to be taken to increase bone strength.
Risk factors for osteopenia include:
- Menopause – lower levels of oestrogen cause the bones to lose calcium and phosphorus quickly, as stated above
- Aging – bone density decreases as we age
- Osteopenia runs in families – check family medical history
- Lifestyle – Not getting enough dietary calcium or vitamin D or sunlight
- Not exercising enough or being overweight
- Smoking
- Excessive alcohol intake
Treatments for osteopenia , especially if your t-score is below -2.0 include, increasing dietary calcium, vitamin D and sunlight exposure, staying active and exercising at least 30 minutes per day, and including resistance/weight bearing exercises. Reducing alcohol intake and stopping smoking will also result in benefits. The closer your t-score is to -2.5, your doctor may consider medication to help strengthen your bones.
What is osteoporosis?
Osteoporosis is the most common bone disorder, and is usually diagnosed after a fragility fracture or a DEXA scan. It can occur due to any of the following:
- Normal peak bone mass during growth was not reached
- An increase in bone breakdown in adulthood
- A decrease in bone buildup in adulthood
The risk factors are the same as osteopenia, however, it is much more serious as the risk of fracture, especially of the hip, is much higher, and it can, and does result in decreased quality of life and death if a fracture is experienced. The structure of the bone becomes much weaker and also less dense, resulting in an increased risk of breaking. Osteoporosis can occur anywhere in the skeleton, but is commonly seen in the hip, spine and wrist.
Usually when osteoporosis is diagnosed, urgent action is required to strengthen bones and prevent fracture, specific medications prescribed from your doctor are required. Medications can work by rectifying the bone remodelling cycle by slowing or blocking the cells that break bone down, so that the bone building cells can continue to strengthen bones. It is also recommended when diagnosed with osteoporosis to follow the lifestyle factors for osteopenia management to further assist in slowing osteoporosis.
The Healthy Bones Australia website has a “Know your bones” online self assessment that allows you to answer some questions and generates a report based on your responses that you can take to your doctor if your risk of osteoporosis is of concern.
The next blog in the Bone Health Series will cover what you can do to prevent bone loss in menopause and beyond. If you are concerned at all about your bone health, connect with me so we can plan to improve your bone density and overall health during this time.
References:
- Australian Government, Australian Institute of Health and Welfare. Osteoporosis https://www.aihw.gov.au/reports/chronic-musculoskeletal-conditions/osteoporosis/contents/what-is-osteoporosis
- Erikson EF, Treatment of osteopenia, Rev Endocr Metab Disord, 2012;13(3):209-223. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3411311/
- Harvard Health Publishing, Osteopenia : when you have weak bones, but not osteoporosis https://www.health.harvard.edu/womens-health/osteopenia-when-you-have-weak-bones-but-not-osteoporosis
- Health direct, Osteopaenia https://www.healthdirect.gov.au/osteopaenia
- Healthy Bones Australia, About Bones https://healthybonesaustralia.org.au/your-bone-health/about-bones/
- Healthy Bones Australia, Osteoporosis Diagnosis https://healthybonesaustralia.org.au/osteoporosis-you/diagnosis/
- John Hopkins Medicine, Bone Densitometry, https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/bone-densitometry
- Kenkre JS & Bassett Jhd, The bone remodelling cycle, Ann Clin Biochem. 2018 May;55(3):308-327. https://journals.sagepub.com/doi/10.1177/0004563218759371?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed
- Newman T, Medical News Today, Bones: All you need to know https://www.medicalnewstoday.com/articles/320444
