Osteoporosis is a disease that causes a decrease in the amount of bone in the skeleton, and deteriorates the bone structure (Pic. 1). These changes weaken the skeleton, leading to an increased chance of breaking or fracturing a bone.

Physiologically, bone deposition by osteoblasts (bone cells that synthesize bone) is continuous and bone absorption occurs where the osteoclasts (type of bone cell that breaks down bone tissue) are active. Except for growing bones, there is an equilibrium between bone deposition and bone absorption; in osteoporosis, the osteoblastic and osteoclastic activities are disproportionate, and the latter predominates.

The skeleton accumulates bone until the age of 30 (Pic. 2), and bone mass is greater in males than in females. After 30, a 0.3% yearly loss occurs. In women, loss is greater during the 10 first post-menopausal years, and it can reach 3% a year. Sedentary women lose more bone.

Osteoporosis is a common condition. According to the World Health Organization (WHO) criteria, 1/3 of the white women older than 65 present osteoporosis; it is estimated that osteoporotic fractures will occur in about 50% of the women older than 75 years.

Though osteoporosis is less common in men, it is estimated that about 1/5 to 1/3 of hip fractures are observed in men and that 60 year-old white men have a 25% probability to have fractures due to osteoporosis.

Types of osteoporosis

Osteoporosis is primary (idiopathic) or secondary. 

Primary (idiopathic) osteoporosis can be type I and type II:

  • In type I, also known as postmenopausal, bone loss occurs quickly and soon after menopause. Predominantly, it is observed in the trabecular bone (makes up the inner layer of the bone and has a spongy, honeycomb-like structure) and is associated to vertebral and radio-distal fractures.
  • Type II, or senile, is related to aging and occurs due to chronic calcium deficiency, increased hormonal activity and reduction in bone formation.

Secondary osteoporosis is a consequence of inflammatory processes as rheumatoid arthritis, endocrine alterations as hyperthyroidism (overactive thyroid gland) and adrenal disorders, multiple myeloma, desuse, use of drugs as heparin, alcohol, vitamin A and corticoids. The corticoids inhibit the intestinal absorption of calcium and increase its urinary elimination, reduce the osteoblast formation and increase de osteoclastic reabsorption.

Diagnosis is based on clinical history, physical examination and tests. History comprehends menopausal age, familial factors, feeding habits, physical activities, coffee intake, cigarette smoking or alcohol drinking. Deformity of the spine is to be observed during physical examination; data about weight, height must be included aiming follow-up. The subsidiary exams are laboratory and image testing; the former are usually normal in primary osteoporosis.

Prevention is the best treatment for osteoporosis; critical elements are the bone mass peak and prevention of postmenopausal reabsorption. The bone mass peak depends on calcium and vitamin D intake, normal menstrual function, and physical activity; most of the therapeutic agents act on bone reabsorption, as anti-reabsorptives. Medications (such as bisphosphonates) are useful in decreasing the risk of future fractures in those who have already sustained a fracture due to osteoporosis.

Symptoms

Clinical signs of osteoporosis show no pain or other symptoms which could point to changes in bone structure, unless a bone fracture is diagnosed. The most common fractures are bones in the spine, hip and wrist. Other bones affected are the shoulder, ribs and pelvis.

Associated diseases

Anorexia nervosa

Anorexia nervosa is a serious psychiatric illness characterized by failure to maintain a minimally normal weight, intense fear of gaining weight or becoming fat, and preoccupations about body shape and weight. Due to insufficient food intake in patients anorexia can lead to malnutrition (diet doesn't contain the right amount of nutrients) or hypovitaminosis (deficiency of one or more vitamins). Nutrition has an important and complex role in maintenance of good bone. High blood acidity may be diet-related, and is a known opposition against the bones. 

Probably more than half of young women with anorexia nervosa develop osteoporosis, and relatively quickly. Males with anorexia nervosa also have osteopenia (weak bones that are still strong enough that they wouldn't break easily during a fall) and osteoporosis. Weight restoration is by far the most effective and evidence-based approach for prevention and treatment of low bone density. Weight gain normalizes hormone levels which play important roles in regulating bone health.

Menstrual cycle disorders

Amenorrhoea is the absence of a menstrual period in a woman of reproductive age. When a woman is experiencing amenorrhoea, an eating disorder, and osteoporosis together, this is called female athlete triad syndrome. A lack of eating causes amenorrhoea and bone loss leading to osteopenia and sometimes progressing to osteoporosis.

Kallmann syndrome

Kallmann syndrome (KS) is a rare genetic condition that is characterized by a failure to start or a failure to complete puberty. Kallmann syndrome occurs due to a failure of the hypothalamus to release gonadotropin-releasing hormone (GnRH) at the appropriate time.

One possible side effect of having KS is the increased risk of developing secondary osteoporosis or osteopenia. Estrogen (females) or testosterone (males) is essential for maintaining bone density. Deficiency in either testosterone or estrogen can increase the rate of bone resorption while at the same time slowing down the rate of bone formation. Overall this can lead to weakened, fragile bones which have a higher tendency to fracture.

Complications

Fractures and related complications are relevant clinical sequelae of osteoporosis; almost all fractures in elderly people are partially due to low bone density. Though any bone is susceptible, they occur mainly in the hip, spine, wrist and ribs.

Hip fractures

In general, hip fracture is a more severe condition: on average 24% of more than 50 year-old patients with hip fractures die within one year after the fracture; 25% of the patients with hip fractures demand prolonged and special care and only one third recovers entirely the independence level they had before the fracture.

Hip fractures occur 2 to 3 times more frequently in women than in men; however, mortality following hip fractures is twice in men as compared to women.

Pain, physical limitation and changes in lifestyle associated to hip and vertebrae fractures can cause psychological symptoms as depression, anxiety, fear or even rage, and hinder recovery.

Spine fractures

Vertebral fractures (Pic. 3) cause important complications as residual pain, reduction in height of the vertebral body and kyphosis (rounded upper back).

Most vertebral fractures are stable so surgical stabilization is not necessary. Progression of deformity and pain, fractures with neurological deficit, stenosis of the vertebral canal or instability due to the fracture are indications for surgical treatment. The anterior column must always be reconstructed, when possible. There are several problems consequent to these fractures, as difficulty in fixation, risk of a fracture adjacent to the fusion, difficulty to evaluate the fusion and a number of associated clinical problems.

Long bone fractures

Most fractures of the long bones are better treated with early surgical stabilization providing quick support for the lower limbs or functional recovery of the upper limbs.

Risk factors

Risks that influence the manifestation of osteoporosis are related to the people (individual) or to the environment they live (environmental).

Low body weight, recent weight loss, previous fractures due to bone fragility, cases of osteoporotic fractures in the family and smoking are considered fracture risk factors. Individuals with any of these factors show a greater risk for fractures, in spite of bone mass. Absence of any of these risk elements reduces fracture risk due to bone fragility. All sites prone to fractures as phalanges, vertebral bodies and long bones have the same probability to show osteoporotic fractures.

Environmental factors are alcohol and tobacco (inhibitors of osteoblast multiplication), caffein (increases calcium excretion), inactivity, malnutrition, diets rich in fibers, proteins and sodium (reduce calcium absorption), nulliparity, amenorrhea due to exercise, early menopause and endocrinopathy (disease of an endocrine gland).

Prevention

At any age, avoid tobacco; alcohol and coffee intake must be moderate; physical activity and adequate amounts of calcium are fundamental.

In peri- and postmenopause, when a familial history of osteoporosis is present, bone densitometry must be yearly controlled. Eventually, hormonal replacement should be instituted and supplementation with calcium and vitamin D is important for the elderly.

As fractures in general occur after falls, shoes with rubber soles should be used; a walking stick provides support and improves walking stability; care must be taken with slippery floors and shoes; walking using only socks must be avoided; supporting bars and rubber floors in the bathroom; small guiding lights to help locomotion during the night; avoid carpets and other objects which can provoke stumbling; improve sight condition.

Generally, osteoporosis or decreased bone density affects almost all women with premature ovarian failure (POF) due to an insufficiency of estrogen (female sex hormones). Premature ovarian failure is the loss of function of the ovaries before age 40. Hormonally, POF is defined by abnormally low levels of estrogen and high levels of follicle-stimulating hormone (FSH), which demonstrate that the ovaries are no longer responding to circulating FSH by producing estrogen and developing fertile eggs. 

In men, osteoporosis is often seen with testosterone deficiency, i.e. low levels of testosterone that stalls sex drive. It can also contribute to erectile dysfunction. Also, testosterone plays an important role in making sperm. Deficiency in testosteorne levels contributes to low sperm count, thus, low sperm count makes it harder to conceive a child.

The progression of osteoporosis can be slowed, stopped, or reversed if getting adequate treatment. 

In general, osteoporosis does not cause infertility. In pregnant women, calcium mobilization and bone resorption are increased and lactation imposes a further increase at the last period of pregnancy. These changes could lead to osteoporosis and fracture in young women. Pregnancy-related osteoporosis is a very rare condition. Its exact prevalence, etiology and pathogenesis are unknown, and risk factors have not been identified, although heparin usage, thyrotoxicosis and genetic background have been suspected.

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Sources

Osteoporosis ―sourced from Wikipedia licensed under CC BY-SA 3.0
Osteoporosis ―by Gali licensed under CC BY-NC 4.0
Bone density and osteoporosis ―sourced from Queensland Government licensed under CC BY 4.0
Osteoporosis ―sourced from Fertilitypedia licensed under CC BY-SA 4.0
615 Age and Bone Mass ―by OpenStax College licensed under CC BY-SA 3.0
Osteoporosis 02 ―by BruceBlaus licensed under CC BY-SA 4.0
Osteoporosis vertebrae ―by Tekksavvy licensed under CC BY-SA 3.0
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