Osteoporosis: causes and increased risk

There are several contributing risk factors and causes. Osteoporosis is defined as a bone disease characterised by low bone mass and subsequent bone fragility. The person who suffers from osteoporosis thus has an increased risk of sustaining a fracture, much as a person with high blood pressure runs an increased risk of getting a stroke.

Risk of course means just that, increased risk. So, people with high blood pressure do not necessarily end up with strokes, and people with osteoporosis do not always end up with fractures. And, like hypertension, osteoporosis can be prevented by timely intervention. The occurrence of osteoporosis varies with age, gender and ethnicity.

  • Age: Osteoporosis is found increasingly in people as they get older. In the West it is thought that more than 50 per cent of white women after the menopause could have lower than normal bone mass, and more than 20 per cent could have osteoporosis. The average age of white women entering the menopause in the West is around 51 years. The number of fractures, particularly in women, increases progressively with age, due largely to osteoporosis.
  • Gender: Women are substantially more affected than men as their peak bone mass (highest level of bone mass ever reached in a person?s life) is lower than that of men in the first instance. They then also lose bone mass far more rapidly than men after the menopause.
  • Ethnicity: Blacks in general have a higher bone mass than Whites and Asians, and in addition their loss of bone mass may be slower than in Whites and Asians. Blacks also show a lower occurrence of osteoporosis.
The three factors mentioned above could possibly be classified more as risk factors than causes of osteoporosis. Other risk factors include:

  • Hormonal factors: Females who did not have children, started menstruating late and stopped menstruating early are at increased risk of getting osteoporosis. Women who did not see their menstrual periods for lengthy spells of time, irrespective of the cause, are also in a high-risk category. Reasons for this latter phenomenon (of not menstruating for a substantial period) include overzealous exercise with lower than normal body fat and surgical removal of the ovaries for whatever reason.
  • Genetic predisposition: Significant here would be a strong family history of osteoporosis. The ethnicity factors mentioned above could also fit into this category.
  • Nutrition: A low calcium intake (dairy products) and low intake of Vitamin D (fish, fish liver oil, egg yoke and butter fat) would be relevant here. The aged are often neglected with poor diets due to a variety of reasons, and this can put them at an even higher risk of getting osteoporosis. High salt and caffeine intake can also aggravate matters.
  • Lifestyle: An inactive lifestyle with alcohol abuse and smoking is bad news for anybody at any time, and definitely so for the person at risk of osteoporosis.
  • Size of body: People of small, slender build are at higher risk than others.

Postmenopausal osteoporosis

As if hot flushes and unpredictable ratty behaviour (!) are not enough, the menopausal woman also starts losing bone mass at an accelerated rate for five years following the start of this period. This is because of declining levels of oestrogen hormone in the blood of women at this stage. The average age at which this happens is 51 years and all women experience it.

Although the effect of this reduction in oestrogen levels varies between women as regards osteoporosis, this drop in hormone concentration constitutes the most important factor in the development of the disease. It is thus imperative that hormone replacement therapy (HRT) is started judiciously in the high-risk patient. This can prevent osteoporosis. In fact, the advantages of hormone replacement therapy on the bones and heart (at least, potentially also on other organs) in the postmenopausal woman presents a compelling argument for all women in this phase to be persuaded to take this form of treatment, not only the high risk patients.

As far as the mechanism of causing osteoporosis goes, it can be said that a drop in levels of oestrogen in the blood brings about an increase in bone turnover and loss at a stage when there is no increase in bone formation. There is therefore a net loss of bone. This accelerated loss of bone occurs for five years after the menopause with a subsequent reduction in bone strength. After this five-year period, bone loss takes place for the rest of a woman?s life but at a slower rate. The significance of starting HRT at the right time is borne out by this reality of accelerated bone loss after the start of the menopause.

The above-mentioned causes and risk factors all fall within the "normal" course of life as it were. Aging, menopause, genetic tendency and gender all belong in this category. There are, however, other disease processes and external factors that might have osteoporosis as a complication of this disease. These are referred to as secondary causes of osteoporosis. Although these causes obviously have to be treated as well, they fall outside the ambit of the usual discussion of prevention and control of osteoporosis. The treatment of these secondary causes revolves around treating the underlying ailment and the improvement of the osteoporosis usually depends on how successfully these afflictions are treated. They include the following:

Disorders of body glands

  • The adrenal glands. These glands in the body are responsible for excreting steroid or "cortisone-like" hormones that are vital in the metabolism of carbohydrates and protein. Overactive adrenal glands cause an excess of cortisone in the blood as the body?s natural cortisone is produced in the adrenals. Cortisone-induced osteoporosis occurs as this substance has a suppressing effect on the number of bone forming cells in the body. Cortisone in addition also has an effect on calcium levels in the blood by reducing the absorption of calcium from the gut.
  • The parathyroid glands. These glands must not be confused with the thyroid gland of which there is only one, while we have four parathyroid glands. These are, as the name indicates, situated near the thyroid gland and secrete a hormone known as parathyroid hormone. This hormone is extremely important in the control of calcium in the bones of the body. An overactive state in the parathyroid glands causes large losses of calcium from the bones and resultant osteoporosis. Indication of this can be found in the very high levels of calcium in the blood.
  • The thyroid gland. An overactive state in the thyroid gland can also contribute to osteoporosis. This condition is not as serious a contributing factor as the overactive parathyroids but is far more common and needs to be kept in mind as a factor in osteoporosis risk.
  • Gastro-intestinal causes. This term describes the stomach and bowel. It comes into the picture, as regards osteoporosis, in that people who have undergone surgery to the stomach with a part of this organ removed, may not be able to absorb enough of the vital bone forming substances from the gut.
  • Bone marrow diseases. In diseases such as leukaemia and myeloma osteoporosis can result from increased loss of bone, thought to be caused by toxic substances released by the cancer process in the body. Recent studies have shown HRT to be problematic in some women, increasing the risk of heart attack, stroke, breast cancer and blood clots. It is important to ensure that both you and your doctor are happy with any treatment indicated.